Removing test for support of nested object of arbitrary type, because neither Document nor BasicDBObject should actually support this use case.
Added assumeTrue of replica set to tests in the ReplicaSet category, so that they don't fail if actually run when there is no replica set.  Otherwise, you get test failures in the IDE when running all tests.
JAVA-416: Use serialized form of a document with lexicographically-sorted keys for equals and hashCode