Add filter support to queryparser [LUCENE-6313]

[asfimport]

Now that Query has the capabilities of Filter, we should let users add clauses of type Occur.FILTER from the query language.

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Migrated from LUCENE-6313 by Robert Muir (@rmuir)
Attachments: LUCENE-6313.patch

[asfimport]

Robert Muir (@rmuir) (migrated from JIRA)

Here is a first patch (with regeneration).

Prefix operator is "#" (consistent with BooleanQuery/BooleanClause). Infix operator is "WHERE" (to me this is intuitive that its required but doesn't impact scoring).

[asfimport]

Michael McCandless (@mikemccand) (migrated from JIRA)

+1

[asfimport]

Adrien Grand (@jpountz) (migrated from JIRA)

+1 to WHERE, I like it too