Add cqlsh completion for IF [NOT] EXISTS in CREATE/DROP USER

Patch by Michał Michalski; review by Tyler Hobbs for CASSANDRA-7611
Add unordered PITR test

Patch by Ala' Alkhaldi, reviewed by brandonwilliams for CASSANDRA-6905
fix test for 2.0
update CL archive comments post-6905
Switch liveRatio-related log messages to DEBUG

ninja-patch by Aleksey Yeschenko for CASSANDRA-7467
Handle KeyboardInterrupt properly in cqlsh

Patch by Jordon Pittier, reviewed by brandonwilliams for CASSANDRA-5481
Merge branch 'cassandra-1.2' into cassandra-2.0
Backport CASSANDRA-6747

patch by yukim; reviewed by krummas for CASSANDRA-7560
Remove shuffle/taketoken.

Patch by brandonwilliams, reviewed by thobbs for CASSANDRA-7601
Remove ability to change num_tokens once set.

Patch by brandonwilliams, reviewed by thobbs for CASSANDRA-7649
Track min/max timestamps for range tombstones.

Patch by marcuse; reviewed by iamaleksey for CASSANDRA-7647
Avoid NPE when listing saved caches directory

Patch by marcuse; reviewed by yukim for CASSANDRA-7632
remove shuffle bat
Ninja: remove buggy test assertion from 2.1

This was fixed by CASSANDRA-7390, but that fix starts with Cassandra
3.0.
Fix truncate to always call flush on table

Patch by Jeremiah Jordan; reviewed by tjake for (CASSANDRA-7511)
SSP doesn't cache seeds forever

Patch by brandonwilliams, reviewed by jbellis for CASSANDRA-7663
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/config/DatabaseDescriptor.java
Remove shuffle/taketoken

Patch by brandonwilliams, reviewed by thobbs for CASSANDRA-7601
Merge branch 'cassandra-1.2' into cassandra-2.0
Set gc_grace_seconds to 7 days for system schema tables

Patch by Tyler Hobbs; review by Aleksey Yeschenko for CASSANDRA-7668