Fix missing key estimate in nodetool

Patch by Lyuben Todorov, reviewed by brandonwilliams for CASSANDRA-8400
Merge branch 'cassandra-2.1' into trunk
Make HHOM.compact synchronized to avoid compacting the same sstables

Patch by marcuse; reviewed by Aleksey Yeschenko for CASSANDRA-8416
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
Add errors setting to stress help, ninja
Merge branch 'cassandra-2.1' into trunk
Throw correct exception when trying to bind a keyspace or table name

patch by Benjamin Lerer; reviewed by Aleksey Yeschenko for
CASSANDRA-6952
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
Fix Accumulator.isEmpty method

patch by slebresne; reviewed by benedict for CASSANDRA-7873
Refuse Paxos operations with more than one pending endpoints

patch by slebresne; reviewed by kohlisankalp for CASSANDRA-8346
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
Merge remote-tracking branch 'origin/trunk' into 8053-udaf-v2
fixes from review (except unit tests)