Refuse unrecognized replication strategy options

patch by dbrosius; reviewed by slebresne for CASSANDRA-4795
Merge branch 'cassandra-1.2' of https://git-wip-us.apache.org/repos/asf/cassandra into cassandra-1.2

Conflicts:
	CHANGES.txt
Fix unfriendly error message (CASSANDRA-5132)
Merge branch 'cassandra-1.2' into trunk