Fixed test cluster scope to be able to run it multiple times if needed
Added ack call when the cluster state has not changed

The missing call could cause a cluster state update to hang in case there is no change no apply
Added support for acknowledgement in update index settings api

Added support for serialization based on version to AcknowledgedResponse. Useful in api that don't support yet the acknowledged flag in the response.
Moved also ack warmer tests to more specific AckTests class

Close #3983
Added support for node acknowledgements in delete mapping api

Closes #3984
Added support for acknowledgements to cluster reroute api

Closes #3985
Added support for acknowledgements to update cluster settings api

As a side note, the internal reroute call is now part of the ack mechanism. That means that if the response contains acknowledged flag, the internal reroute that was eventually issued was acknowledged too. Also, even if the request is not acknowledged, the reroute is issued before returning, which means that there is no need to manually call reroute afterwards to make sure the new settings are immediately applied.

Closes #3995
Improving test stability for CompletionTests

Randomized testing caught an issue showing that the test should
flush after indexing a document, as always the same document is
indexed.
[DOCS] Extending setup as a service documentation

* Tell people to use ES_JAVA_OPTS for es.node.name or similar parameters
* Showing a simple way to install Oracle JDK on ubuntu/debian

Closes #3999
Added getters for fs.path, fs.mount and fs.dev in node stats api

Closes #4004
explicitly enable http when running plugin tests

add an option to force a setting when building a node, overriding if its explicitly set as system property
Also resend shard started message if shard state is in POST_RECOVERY and master thinks it's initializing.

Closes #4009
Add back hashed BytesValues optimization that got lost in a previous commit.

Some FieldData consumers require hash values per byte. We provide an optimization
that allows to cache the hashes internally if the consumer knows that they are needed
this optimization got lost in a previous commit. This commit adds them back and folds
the dedicated method into AtomicFieldData#getBytesValues(true|false)
minor improvement to FullRollingRestartTests failure output
throw index already exists failure when it exists as alias on creation
make sure to throw the already exists exception, so when indexing into an alias, and it has not propagated yet through the cluster state, it will end up being ignored if it already exists
[DOCS] Fixed a typo
[DOCS] Added a version flag to percolation
indices cluster state service should execute as one of the first listeners
its preferable to execute the indices cluster state service as quickly as possible, as one of the first listeners, so it will apply the cluster state to the local state
potentially, it should even execute before it state is "visible" (through the state call), but that's another change...
Add _cat/allocation/{nodes}.

Visualizes how shards distribute across the cluster.

% curl localhost:9200/_cat/allocation
shards diskUsed diskAvail diskRatio ip        node
     2   85.6gb   379.4gb     22.6% 127.0.0.1 MacTaggert, Moira
     2   85.6gb   379.4gb     22.6% 127.0.0.1 Jarvis, Edwin

% curl localhost:9200/_cat/allocation/Jar\*
shards diskUsed diskAvail diskRatio ip        node
     2   85.6gb   379.4gb     22.6% 127.0.0.1 Jarvis, Edwin
Add a GetFieldMapping API

This new API allows to get the mapping for a specific set of fields rather than get the whole index mapping and traverse it.
The fields to be retrieved can be specified by their full path, index name and field name and will be resolved in this order.
In case multiple field match, the first one will be returned.

Since we are now generating the output (rather then fall back to the stored mapping), you can specify `include_defaults`=true on the request to have default values returned.

Closes #3941
Add node name & ip to _cat/recovery.

Closes #4016.