Support NaN and Infinity as float constants

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6003
Don't allow describe on CQL3 table in CLI ever

patch by slebresne; reviewed by iamaleksey for CASSANDRA-5750
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
Update version for 2.0.3 release