Group bucket and action bucket support

Following changes are made to support group buckets and action bucket:

1) Changed all keys to string as MongoIPC can send data with strings as key only.
2) group_type was not being sent from RFServer to RFProxy by IPC, fixed it.
3) Group commands parsing at RFProxy.
4) Parsing of different bucket and action attributes at RFProxy.

Signed-off-by: Srijan Mishra <srijan23mishra@gmail.com>