Meter Band configuration support

Following changes are made to send meter_band with MeterMod message from rfserver to rfproxy and parse the message at rfproxy:

1) RFProtocol: MongoIPC supports only string keys in the message being sent so updated band types being used as keys in meter bands to be inserted as strings.
2) Added all meter commands parsing in rfproxy.
3) Meter bands parsing: Attributes are sent as binary but openflow switch accepts only integers so parsed them to integer values.

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