Use Package Resource Api to access data files

As part of the efforts to make the installation more generic, I've removed all the attempts to install helpers in global paths (so package managers will have to deal with it).

Until now, bundle was considered a special case, and it has its resource paths hardcoded. Now that we're considering the possibility of having the --install-data set to any path, we should remove the references to the data paths, and use the Package Resource api that setuptools provides instead.

http://peak.telecommunity.com/DevCenter/PythonEggs#accessing-package-resources

Note: We should check that bitmask-root is indeed only root-writeable before trying to execute it, from /opt or any other location.

(from redmine: created on 2015-01-29, relates #6507 (closed))