Revert "Prefer string slices over boxed strings in path filters."
Since the HashMap should own the string, it should actually be boxed,
otherwise we will run into lifetime issues later on.

This reverts commit ea241b9f30a0ceea623da9c62e53f280a511add0.
Make PathFilter public.

Signed-off-by: Lewis Gunsch <lewis@gunsch.ca>
Put path module sub-module includes in mod.rs.

Signed-off-by: Lewis Gunsch <lewis@gunsch.ca>
Implement PathLoader apply_filter, and add_many methods.

Signed-off-by: Lewis Gunsch <lewis@gunsch.ca>
Re-export PathFilter and PathLoader in the path module.

Signed-off-by: Lewis Gunsch <lewis@gunsch.ca>