Updated Analyzing/Fuzzysuggester from lucene trunk

* Minor alignments (like setter to ctor)
* FuzzySuggester has a unicode aware flag, which is not exposed in the fuzzy completion request parameters
* Made XAnalyzingSuggester flags (PAYLOAD_SEP, END_BYTE, SEP_LABEL) to be written into the postings format, so we can retain backwards compatibility
* The above change also implies, that these flags can be set per instantiated XAnalyzingSuggester
* CompletionPostingsFormatTest now uses a randomProvider for writing data to check for bwc
Randomized CompletionSuggestSearchTests
Added unit test for current completion postingsformat
Make parsing of uri and body parameters consistent with single term vector api

uri parameters were not all parsed for the multi term vector request. This commit
makes sure that all parameters are parsed and used when creating the requests for the
multi term vector request.

In order to simplify both code and json request, the request structure now allows
two ways to use multi term vectors:

1. Give all parameters for each document requested in the docs array like this:

```
{
   "docs": [
      {
         "_index": "testidx",
         "_type": "test",
         "_id": "2",
         "terms": [
            "fox"
         ],
         "term_statistics": true
      },
      {
         "_index": "testidx",
         "_type": "test",
         "_id": "1",
         "terms": [
            "quick",
            "brown"
         ],
         "term_statistics": false
      }
   ]
}
```

2. Define a list of ids and give parameters in a separate parameters object like this:

```
{
   "ids": [
      "1",
      "2"
   ],
   "parameters": {
      "_index": "testidx",
      "_type": "test",
      "terms": [
         "brown"
      ]
   }
}
```

uri parameters are global parameters that are set for both cases. They are overwritten
by parameter definitions in the body.

Also, this commit adds the missing setParent(..) and setPreference(..) to TermVectorRequestBuilder.
[DOC] add doc for multi term vector api

closes #3998
Fix issue 3989

Multi term vector request never returned if shards for all requested documents
were non existent.

closes #3989