Update version number for 2.1.0-rc7
Better err msg when condition is set on PK column

Patch by Tyler Hobbs; review by Sylvain Lebresne for CASSANDRA-7804
Merge branch 'cassandra-2.0' into cassandra-2.1.0
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java
Merge branch 'cassandra-2.1.0' into cassandra-2.1