Add warning on collection limitations in CQL doc
Change snapshot response message verb

to make sure response do not get dropped

patch by yukim; reviewed by jbellis for CASSANDRA-6415
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/service/SnapshotVerbHandler.java
Merge branch 'cassandra-2.0' into trunk
Multithreaded commitlog
patch by Benedict Elliot Smith; reviewed by jbellis for CASSANDRA-3578