Need QueryParser support for BooleanQuery.minNrShouldMatch [LUCENE-466]

Attached 2 new classes:

1) CoordConstrainedBooleanQuery
A boolean query that only matches if a specified number of the contained clauses
match. An example use might be a query that returns a list of books where ANY 2
people from a list of people were co-authors, eg:
"Lucene In Action" would match ("Erik Hatcher" "Otis Gospodnetić" "Mark Harwood"
"Doug Cutting") with a minRequiredOverlap of 2 because Otis and Erik wrote that.
The book "Java Development with Ant" would not match because only 1 element in
the list (Erik) was selected.

2) CustomQueryParserExample
A customised QueryParser that allows definition of
CoordConstrainedBooleanQueries. The solution (mis)uses fieldnames to pass
parameters to the custom query.

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Migrated from [LUCENE-466](https://issues.apache.org/jira/browse/LUCENE-466) by Mark Harwood (@markharwood), 1 vote, updated Mar 19 2014
Environment:
```
Operating System: other
Platform: Other
```

Linked issues:
- #1473

Start by reading QueryParser and BooleanQuery's minNrShouldMatch behavior, then inspect the described CoordConstrainedBooleanQuery and CustomQueryParserExample classes. Determine how QueryParser should represent the minimum required overlap without relying on field names. Done means the parser can express the requested constrained query and its matching behavior is covered by tests.

Written by the indexing model from the issue text.