Changes related to flowtable generic implementation.

Changes related to flowtable generic implementation.

Few modifications to the flowtable generic

prefinal commit.
Generic flowtable implementation

Generic flow table will maintain hash for flow mask so it is no longer
required to maintain wildcard bucket.
Generic flowtable implementation.

Addressed review comments.
Merge into master from pull request #11:
Initial version of generic flow table implemenration (https://github.com/floodlight/ivs/pull/11)