urlutil: add a `copy` method to `path
This will be useful when inheriting from multiple path at the same time.
Differential Revision: https://phab.mercurial-scm.org/D10445
template: add a `paths` field to all entry in peerurls
This make it possible to display multiple path per name in the near future.
Differential Revision: https://phab.mercurial-scm.org/D10444