Added statistical facet to term facet in SimpleNestedTests

The test now uses a statistical facet plus a filter facet on nested documents.
rename variable and add comment about TopDocs#merge
Removed useless TODO
Added the "pattern_capture" token filter from Lucene 4.4

The XPatternCaptureGroupTokenFilter.java file can be removed once we
upgrade to Lucene 4.4.

This change required the addition of the commaDelimited flag to getAsArray()
to disable parsing strings as comma-delimited values.

Closes #3340
Add the ability to ignore or fail on numeric fields when executing more-like-this or fuzzy-like-this queries.

More-like-this and fuzzy-like-this queries expect analyzers which are able to
generate character terms (CharTermAttribute), so unfortunately this doesn't
work with analyzers which generate binary-only terms (BinaryTermAttribute,
the default CharTermAttribute impl being a special BinaryTermAttribute) such as
our analyzers for numeric fields (byte, short, integer, long, float, double but
also date and ip).

To work around this issue, this commits adds a fail_on_unsupported_field
parameter to the more-like-this and fuzzy-like-this parsers. When this parameter
is false, numeric fields will just be ignored and when it is true, an error will
be returned, saying that these queries don't support numeric fields. By default,
this setting is true but the mlt API sets it to true in order not to fail on
documents which contain numeric fields.

Close #3252
Analysis: update ThaiAnalyzerProvider to use custom stopwords setting