COUCHDB-1512 - Validate bind address
COUCHDB-1512 - Validate bind address

This patch validate the bind_address value before attempting to bind
the mochiweb socket, giving an 'invalid_bind_address' error. This
should help users who have specified a hostname or made a typo as the
original error was less helpful.

Fix as suggested by Dave Cottlehuber.

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb