Properly reject operations on list index

patch by slebresne; reviewed by thobbs for CASSANDRA-7499
Merge branch 'cassandra-2.0' into cassandra-2.1.0

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

Conflicts:
	CHANGES.txt
Support list index operation with conditions

patch by slebresne; reviewed by thobbs for CASSANDRA-7499