Invalidate key cache on table drop

patch by thobbs; reviewed by slebresne for CASSANDRA-6525
Fix flapping RecoveryManagerTest

patch by benedict; reviewed by jbellis for CASSANDRA-7084
Add missing iso8601 patterns for date strings

patch by chander; reviewed by slebresne for CASSANDRA-6973
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/db/ColumnFamilyStore.java
	src/java/org/apache/cassandra/db/commitlog/CommitLogAllocator.java