SB REST plugin - initial classifier support

+ listener to ACL datastore
+ put task for ACL (PUT on URL from sfc_agent.py)

When any change is detected in ACL datastore, all classifiers are examined.
The procedure is following:
1. Get all Clasiffiers
2. For each SFF listed in a Classifier
3. Submit (PUT) ACL used in the Classifier to SFF

The functionality needs to be improved according to discussion.

Change-Id: Ib44c4430ef9b65f0140c49ca48e6ed9a8ad6ba9c
Signed-off-by: Andrej Kincel <akincel@cisco.com>