Implement tunnel endpoint declaration.
  * Rearrange model to implement tunnel endpoints and allow other
    non-network endpoints
  * Fix some issues with model ownership and object types
  * Implement tunnelepmanager that can discover local IP address and
    write the appropriate object to the MODB.

Change-Id: I8c267e6d7c9aa9e9392993563527696f2fb382d4
Signed-off-by: Rob Adams <readams@readams.net>