Percolator should cache index field data instances.

Before the index reader used by the percolator didn't allow to register a CoreCloseListener, but now it does, making it safe to cache index field data cache entries.
Creating field data structures is relatively expensive and caching them can save a lot of noise if many queries are evaluated in a percolator call.

Closes #6806
Closes #7081
[TEST] better failure message when back location is missing
MultiGet & MultiTermVector api: fail when using no routing and an alias to an index that has routing required (for that doc type)

Made sure that the routing required check is performed against the concrete index, added use of aliases to existing routing tests.

Taken the change to unify the failure message as well to this form: routing is required for [" + index + "]/[" + type + "]/[" + id + "]

Closes #7145
Core: simultaneous create/delete against same id can cause silently inconsistent replica

If simultaneous create & delete operations arrive against the same id,
it's possible that primary and replica see those operations in
different orders, which may result in replica throwing
DocumentAlreadyExistsException when the primary didn't which would
lead to replica being inconsistent (missing a document that primary
had indexed).

This push fixes the issue, by never throwing DAEE from the replica on
create.

Closes #7146 #7142
Transport: better categorization for transport actions

Our transport relies on action names that tell what we need to do with each message received and sent on any node, together with the content of the request itself.
The action names could use a better categorization and more consistent naming though, the following are the categories introduced with this commit:

- indices: for all the apis that execute against indices
  - admin: for the apis that allow to perform administration tasks against indices
  - data: for the apis that are about data
    - read: apis that read data
    - write: apis that write data
    - benchmark: apis that run benchmarks

- cluster: for all the cluster apis
  - admin: for the cluster apis that allow to perform administration tasks
  - monitor: for the cluster apis that allow to monitor the system

- internal: for all the internal actions that are used from node to node but not directly exposed to users

The change is applied in a backwards compatible manner: we keep the mapping old-to-new action name around, and when receiving a message, depending on the version of the node we receive it from, we use the received action name or we convert it to the previous version (old to new if version < 1.4). When sending a message, depending on the version of the node we talk to, we use the updated action or we convert it to the previous version (new to old if version < 1.4).
For the cases where we don't know the version of the node we talk to, namely unicast ping, transport client nodes info and transport client sniff mode (which calls cluster state), we just use a lower bound for the version, thus we will always use the old action name, which can be understood by both old nodes and new nodes.

Added test that enforces known updated categories for transport action names and test that verifies all action names have a pre 1.4 version for bw compatibility

Added backwards compatibility tests for unicast and transport client in sniff mode, the one for the ordinary transport client (which calls nodes info) is implicit as it's used all the time in our bw comp tests.
Added also backwards comp test that sends an empty message to any of the registered transport handler exposed by older nodes and verifies that what gets back is not ActionNotFoundTransportException, which would mean that there is a problem in the actions mappings.

Added TestCluster#getClusterName abstract method and allow to retrieve externalTransportAddress and internalCluster from CompositeTestCluster.

Closes #7105
Search: add time zone setting for relative date math in range filter/query

Filters and Queries now supports `time_zone` parameter which defines which time zone should be applied to the query or filter to convert it to UTC time based value.

When applied on `date` fields the `range` filter and queries accept also a `time_zone` parameter.

The `time_zone` parameter will be applied to your input lower and upper bounds and will move them to UTC time based date:

[source,js]
--------------------------------------------------
{
    "constant_score": {
        "filter": {
            "range" : {
                "born" : {
                    "gte": "2012-01-01",
                    "lte": "now",
                    "time_zone": "+1:00"
                }
            }
        }
    }
}

{
    "range" : {
        "born" : {
            "gte": "2012-01-01",
            "lte": "now",
            "time_zone": "+1:00"
        }
    }
}
--------------------------------------------------

In the above examples, `gte` will be actually moved to `2011-12-31T23:00:00` UTC date.

NOTE: if you give a date with a timezone explicitly defined and use the `time_zone` parameter, `time_zone` will be
ignored. For example, setting `from` to `2012-01-01T00:00:00+01:00` with `"time_zone":"+10:00"` will still use `+01:00` time zone.

Closes #3729.
[TEST] Fixed action names bw comp tests, action not found is expected for newly added exists actions
[TEST] Fixed GetTermVectorTests, added missing break statements in randomization switch
Added custom transport client settings to test infra

It's now possible to define the additional customesettings for transport clients by extending `transportClientSettings` callback method on `ElasticsearchIntegrationTest`.
Aggregations: key_as_string only shown when format specified in terms agg

The key_as_string field is now not shown in the terms aggregation for long and double fields unless the format parameter is specified

Closes #7125
[TEST} make sure unicast bw comp test uses specifically set transport port and properly configure unicast hosts

Added also assertBusy block needed since we test the local cluster state on each node, not only on the master node.
add Proxy setting for using plugin command

Closes #7150
[TEST] add explicit options to no master tests
Make "cluster.routing.allocation.allow_rebalance" a dynamic setting

Also makes it a static constant and changes all tests to use it instead
of a string.

Fixes #7092
[TEST] increase ack timeout on large cluster
when we have a small machine running it with randmoized larger number of nodes (5), we need more time to process it
Resolve wording inconsistency

AND and OR filter docs talk about different targets for the operators. I
believe that both should be described in terms of modifying other 'filters'.
I also added articles for easier (human) parsing. This fixes #4762

Closes #7165
CORS: Allowed to configure allow-credentials header to work via SSL

This adds support to return the "Access-Control-Allow-Credentials" header
if needed, so CORS will work flawlessly with authenticated applications.

Closes #6380
Query Cache: Support shard level query response caching

The query cache allow to cache the (binary serialized) response of the shard level query phase execution based on the actual request as the key. The cache is fully coherent with the semantics of NRT, with a refresh (that actually ended up refreshing) causing previous cached entries on the relevant shard to be invalidated and eventually evicted.

This change enables query caching as an opt in index level setting, called `index.cache.query.enable` and defaults to `false`. The setting can be changed dynamically on an index. The cache is only enabled for search requests with search_type count.

The indices query cache is a node level query cache. The `indices.cache.query.size` controls what is the size (bytes wise) the cache will take, and defaults to `1%` of the heap. Note, this cache is very effective with small values in it already. There is also the advanced option to set `indices.cache.query.expire` that allow to control after a certain time of inaccessibility the cache will be evicted.

Note, the request takes the search "body" as is (bytes), and uses it as the key. This means same JSON but with different key order will constitute different cache entries.

This change includes basic stats (shard level, index/indices level, and node level) for the query cache, showing how much is used and eviction rates.

While this is a good first step, and the goal is to get it in, there are a few things that would be great additions to this work, but they can be done as additional pull requests:

- More stats, specifically cache hit and cache miss, per shard.
- Request level flag, defaults to "not set" (inheriting what the setting is).
- Allowing to change the cache size using the cluster update settings API
- Consider enabling the cache to query phase also when asking hits are involved, note, this will only include the "top docs", not the actual hits.
- See if there is a performant manner to solve the "out of order" of keys in the JSON case.
- Maybe introduce a filter element, that is outside of the request, that is checked, and if it matches all docs in a shard, will not be used as part of the key. This will help with time based indices and moving windows for shards that fall "inside" the window to be more effective caching wise.
- Add a more infra level support in search context that allows for any element to mark the search as non deterministic (on top of the support for "now"), and use it to not cache search responses.

closes #7161
Update API enhancement - add support for scripted upserts.
In the case of inserts the UpdateHelper class will now allow the script used to apply updates to run on the upsert doc provided by clients. This allows the logic for managing the internal state of the data item to be managed by the script and is not reliant on clients performing the initialisation of data structures managed by the script.

Closes #7143
[Query Cache] Add a request level flag to control query cache
A request level flag, defaults to be unset, to control the query cache. When not set, it defaults to the index level settings, when explicitly set, will override the index level setting
closes #7167