Statistics loadable / installable in Karaf

 - created new feature odl-openflowjava-stats in order to ensure correct
   module start
 - created new project openflowjava-config to properly store and delagate
   statistics config file
 - removed stats-collection as a service from configuration xml

Change-Id: If2b94c4ec9bf2a2c8157eaad546672df6e1d1500
Signed-off-by: Michal Polkorab <michal.polkorab@pantheon.sk>