Added Controller._path_to_annotation().

The method is a developer utility.

The method tells you where a path comes from.

Example:

    >>> path = '/Users/trevorbaca/Documents/scores/traiettorie/stylesheets/foo.ily'
    >>> score_manager._path_to_annotation(path)
    'Traiettorie inargentate'

Note that what's returned here is the typographically correct score title.
Behind the scenes a score package manager is instantiated to get title
metadata.