Give read access to system.schema_usertypes to all authenticated users

patch by Mike Adamson; reviewed by Aleksey Yeschenko for CASSANDRA-7578

Conflicts:
	CHANGES.txt
Fix ReversedType(DateType) mapping to native protocol

patch by Karl Rieb; reviewed by Aleksey Yeschenko for CASSANDRA-7576

Conflicts:
	CHANGES.txt
Fix native protocol drop user type notification

patch by Aleksey Yeschenko; reviewed by Tyler Hobbs for CASSANDRA-7571

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1.0' into cassandra-2.1