SERVER-6400 - framework and start of Matcher replacement.  using Matcher2 name
SERVER-6400 - port more old tests
SERVER-6400 - more matcher tests using both versions
SERVER-6400 - some style improvements for Matcher2
SERVER-6400 rename *Expression* to *MatchExpression* to avoid conflict
SERVER-6400 - keep a real BSONObj in Matcher2, not a reference