configurable bloom filters (like hbase)

[Radim Kolar]

i have problem with large CF (about 200 billions entries per node). 
While i can configure index_interval to lower memory requirements, i 
still have to stick with huge bloom filters.

Ideal would be to have bloom filters configurable like in hbase. 
Cassandra standard is about 1.05% false possitive but in my case i would 
be fine even with 20% false positive rate. Data are not often read back. 
Most of them will be never read before they expire via TTL.