Check that key_aliases/column_aliases exists before using them
Patch by brandonwilliams, reviewed by iamaleksey for CASSANDRA-6589
Merge branch 'cassandra-2.0' into trunk
fix indentation
Merge branch 'cassandra-2.0' into trunk
Pre-6504 cleanup and fixups

patch by Aleksey Yeschenko; reviewed by Sylvain Lebresne for
CASSANDRA-6504