mcf: Add support to enable buildhistory repository

* BUILDHISTORY_COMMIT is set to 1 when buildhistory is enabled
* BUILDHISTORY_AUTHOR assignment is generated in local.conf if
  buildhistory author is provided, otherwise it will use author
  from global git config

Change-Id: If75ed6dc0bc79df66588a2e6eb923af43e5e58a7
Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@palm.com>