[MONDRIAN-1694]  Mondrian applies non empty to native filter when "matches" is used.

This change adds a check for NonEmpty prior to applying a context constraint when evaluating a native filter.  A SqlContextConstraint forces a join to the fact table,
which will drop any tuples not associated with fact data.
Merge pull request #169 from mkambol/1694

[MONDRIAN-1694]  Mondrian applies non empty to native filter when "matches" is used.