Fixed a bug when NetworkTopologyStrategy is used.

Although the Cassandra documentation implies that the
`replication_factor` parameter would be ignored in this case its
presence will cause an error when creating a keyspace using
NetworkTopologyStrategy.
Test demonstrating regression in querying with dates
Merge branch 'model-query-issue' of https://github.com/dokai/cqlengine into issue-130
removing double replication strategy fix
fixing polymorphic test
fixing to_database behavior for functions