Don't reduce twice if failure occurs.
Refactor term vector api

This is necessary to allow adding a mult term vector request
Multi term vector request
--------------------------

This feature allows to retrieve [term vectors](https://github.com/elasticsearch/elasticsearch/issues/3114) for a list of documents. The json request has exactly the same [format](https://github.com/elasticsearch/elasticsearch/issues/3484) as the ```_termvectors``` endpoint

It use it, call

```
curl -XGET 'http://localhost:9200/index/type/_mtermvectors' -d '{
    "fields": [
        "field1",
        "field2",
        ...
    ],
    "ids": [
        "docId1",
        "docId2",
        ...
    ],
    "offsets": false|true,
    "payloads": false|true,
    "positions": false|true,
    "term_statistics": false|true,
    "field_statistics": false|true
}'

```

The return format is an array, each entry of which conatins the term vector response for one document:

```
{
   "docs": [
      {
         "_index": "index",
         "_type": "type",
         "_id": "docId1",
         "_version": 1,
         "exists": true,
         "term_vectors": {
         	...
         }
      },
      {
         "_index": "index",
         "_type": "type",
         "_id": "docId2",
         "_version": 1,
         "exists": true,
         "term_vectors": {
         ...
         }
      }
   ]
}
```

Note that, like term vectors, the mult term vectors request will silenty skip over documents that have no term vectors stored in the index and will simply return an empty response in this case.

Closes #3536
Added extra logging
improve search while create test
- improve the test to be more re-creatable
- have tests for various number of replica counts, to check if failures are caused by searching on replicas that might not have been refreshed yet
- improve test to test explicit index creation, and index creation caused by index operation
- have an initial search go to _primary, to check if failure fails when searching on replica because it missed a refresh
Improve refresh logic when replica move to started
closes #3573
Only use the client variable and don't use client from client() in percolator test
Small cleanup
Added highlighter to percolate api.

The highlighter in the percolate api highlights snippets in the document being percolated. If highlighting is enabled then foreach matching query, highlight snippets will be generated.
All highlight options that are supported via the search api are also supported in the percolate api, since the percolate api embeds the same highlighter infrastructure as the search api.
The `size` option is a required option if highlighting is specified in the percolate api, other than that the `highlight`request part can just be placed in the percolate api request body.

Closes #3574
Rename multi percolate item actions:
count_percolate -> count
percolate_existing_doc -> percolate
count_percolate_existing_doc -> count

If header contains `id` field, then it will automatically be percolation  an existing document.
No test is simple
Simplified percolate reduce logic and the percolator recovery test
Configurable sort order for missing string values.

This commit allows for configuring the sort order of missing values in BytesRef
comparators (used for strings) with the following options:
 - _first: missing values will appear in the first positions,
 - _last: missing values will appear in the last positions (default),
 - <any value>: documents with missing sort value will use the given value when
   sorting.

Since the default is _last, sorting by string value will have a different
behavior than in previous versions of elasticsearch which used to insert missing
value in the first positions when sorting in ascending order.

Implementation notes:
 - Nested sorting is supported through the implementation of
   NestedWrappableComparator,
 - BytesRefValComparator was mostly broken since no field data implementation
   was using it, it is now tested through NoOrdinalsStringFieldDataTests,
 - Specialized BytesRefOrdValComparators have been removed now that the ordinals
   rely on packed arrays instead of raw arrays,
 - Field data tests hierarchy has been changed so that the numeric tests don't
   inherit from the string tests anymore,
 - When _first or _last is used, internally the comparators are told to use
   null or BytesRefFieldComparatorSource.MAX_TERM to replace missing values
   (depending on the sort order),
 - BytesRefValComparator just replaces missing values with the provided value
   and uses them for comparisons,
 - BytesRefOrdValComparator multiplies ordinals by 4 so that it can find
   ordinals for the missing value and the bottom value which are directly
   comparable with the segment ordinals. For example, if the segment values and
   ordinals are (a,1) and (b,2), they will be stored internally as (a,4) and
   (b,8) and if the missing value is 'ab', it will be assigned 6 as an ordinal,
   since it is between 'a' and 'b'. Then if the bottom value is 'abc', it will
   be assigned 7 as an ordinal since if it between 'ab' and 'b'.

Closes #896
Make sure preference isn't null
Fixed order of parameters when calling byteSizeField and timeValueField methods (introduced with #3432 - support for human readable flag)
Added log info on test finished
Add more tests for Zone Awareness
MultiTermVectorsAction was wrongly registered under mget
Fixed extraction of site plugins downloaded from github, so that we skip the top-level folder and we place the files directly under the _site folder

Closes #3551