CBD-697: Move Couchbase specific file

Move the Couchbase specific geocouch_file module to its own directory
in order to prepare a sane build system for both, Couchbase and
Apache CouchDB.

Change-Id: I812b416c57161fcabe02dcff665c6356653770fb
Reviewed-on: http://review.couchbase.org/22989
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>