Make batchlog replay asynchronous

patch by Oleg Anastasyev; reviewed by Aleksey Yeschenko for
CASSANDRA-6134
Merge branch 'cassandra-2.1' into trunk
Support authentication in CqlRecordReader

Patch by Jacek Lewandowski, reviewed by Alex Liu for CASSANDRA-7221
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
remove unused classes

patch by dshelepov reviewed by dbrosius for cassandra-7197
fix CHANGES
Merge branch 'cassandra-2.1' into trunk
Followup to 6916, don't try to snapshot readers that are opened early.

Patch by benedict; reviewed by marcuse for CASSANDRA-6916.
Merge branch 'cassandra-2.1' into trunk