DATAMONGO-1093 - Added hashCode() and equals(…) in BasicQuery.

We now have equals(…) and hashCode(…) methods on BasicQuery. Previously we solely relied on Query.hashCode()/equals(…) which didn't consider the fields of BasicQuery.

Introduced equals verifier library to automatically test equals contracts.
Added some additional test cases to BasicQueryUnitTests.

Original pull request: #252.