Made config/mdsal/netconf features non-cyclic

We previously had some cross dependency between config-features and
netconf-features.  This is highly undesirable because it
precludes folks being able to simply have a maven dependency for the
one feature they want and requires enumerating *all* the feature
files.

This fixes that by pulling out

features/config-netty
features/config-persister
from
features/config

So the dependency graph is now non-cyclic:

config-netty -> config-persister
config-persister -> (netconf,config)
netconf -> (config,protocol-framework)

Change-Id: Ie662df40bd6985e2ecd4280596ddafc947e5edd0
Signed-off-by: Ed Warnicke <eaw@cisco.com>