Remove bogus validation post-6855
Fix IllegalArgumentException in CqlStorage

patch by slebresne; reviewed by driftx for CASSANDRA-7287
Bump CQL version to 3.1.7, update CQL docs

Follow up for CASSANDRA-6875
Merge branch 'cassandra-2.0' into cassandra-2.1
Support nul/non-existant fields in UDT

patch by slebresne; reviewed by iamaleskey for CASSANDRA-7206
Make UserType extend TupleType
Wire tuple types to the native protocol
Support tuple types and literals