Unified implementations of BrokerService Proxies which are provided to Consumers...

Unified implementations of BrokerService Proxies which are provided to Consumers/Producers.

    - Added AbstractBrokerServiceProxy which is Autocloseable,
      and specific for each provider.

      This proxy is convenience wrapper, which keeps track of all
      object listeners retrieved from proxied service,
      so when proxy is closed (deregistered) all registrations
      are also removed.

    - Added concrete implementations of AbstractBrokerServiceProxy
      for Data*Services, Notification*Services and SchemaService
    - Updated implementation of SchemaService to provide notifications
      when new bundle with model is loaded.

Change-Id: I92b67dcb7f376fcf05ea41213aac719c7a3e902e
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>