CCBC-234 Add lcb_cntl command to determine source of configuration

Change-Id: I2ead6c25cc6011ab5b5334ad707dd47ff0d20eb4
Reviewed-on: http://review.couchbase.org/33044
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>