CCBC-386: mcserver: Organize api calls better

- Move most of functions unused outside mcserver to mcserver.c itself,
  rather than exposing it as an API
- Provide some more documentation for functions

Change-Id: I2933d9e6b87ba9310ec77929399c71b6d8444668
Reviewed-on: http://review.couchbase.org/38292
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>