Add fetching of git/hg repositories

Review Request #9502 — Created Jan. 20, 2018 and submitted — Latest diff uploaded




If there are a lot of Review Bot worker it will be
very expensive to maintain a repository configuration
manually. Since a reviewboard instance already knows
the configuration it is now be possible to configure
multiple reviewboard instances and let the Review Bot
fetch git and hg repositories automatically.

If a repository has a "path" or "mirror_path" that
can be access locally or has a scheme starting with
"http" or "git" it will be added to known repository.

Added some repositories in reviewboard with path
and mirror_path. Some with non-existing local path
and mirror_path with "http" scheme.

Saw that the Review Bot finds all accessible
repositories are added correctly.

Tested with and without authentication.