Track maximum ttl and use to expire entire sstables

patch by krummas; reviewed by slebresne for CASSANDRA-5528
Update offline scrub for 1.0-> 1.1 directory structure
patch by Omid Aladini; reviewed by Marcus Eriksson for CASSANDRA-5195)
merge from 1.1
Merge branch 'cassandra-1.2' into trunk
newer 5195 patch
Merge branch 'cassandra-1.1' into cassandra-1.2
Merge branch 'cassandra-1.2' into trunk
inline IAsyncResult
comment
generify AsyncRepairCallback
make AsyncResult extend IAsyncCallback; inline IMessageCallback
rename
r/m redundant branching
fix unit test
patch by Marcus Eriksson
prevent NPE when there is nothing to do
add description to realclean
Merge branch 'cassandra-1.2' into trunk
upgrade to snakeyaml 1.11
add assert that compactionstrategy != null
rename AntiEntropyService -> ActiveRepairService