asserting that an auto-boxed primitive is not null is pointless
Allow removing snapshots of no-longer-existing CFs
patch by Lyuben Todorov and Mikhail Stepura for CASSANDRA-6418
Merge branch 'cassandra-2.0' into trunk
Rename RowMutation->Mutation in preparation for Row->Partition
cql注释
Merge branch 'trunk' of http://git-wip-us.apache.org/repos/asf/cassandra into trunk

Conflicts:
	src/java/org/apache/cassandra/config/CFMetaData.java
	src/java/org/apache/cassandra/config/ColumnDefinition.java
	src/java/org/apache/cassandra/config/KSMetaData.java
	src/java/org/apache/cassandra/db/DefsTables.java
	src/java/org/apache/cassandra/db/Mutation.java
	src/java/org/apache/cassandra/service/MigrationManager.java
	src/java/org/apache/cassandra/service/RowDataResolver.java