This updates celerity_mapper.php to be aware of and embed library information. It also enforces a directory structure for libphutil modules, which involves webroot sitting outside the module itself. See the code comments for the actual structure (hint: it is identical to the way Phabricator is organised now).

Ran celerity_mapper.php on the Phabricator code base and could view the dashboard normally. Saw the module information embedded in the map. Ran the mapper for an external libphutil module and saw it generate the map correctly for it's resources as well.