Place format-related tests in their own file

Change-Id: I0f6efef8163e20a0765ff143cdc3bbba454361b1
Reviewed-on: http://review.couchbase.org/28230
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>