Girocco/Config.pm: add a Bitbucket mirror source

Girocco/Config.pm: add a Bitbucket mirror source

Originally Bitbucket was hg only.  Then Atlassian acquired Bitbucket.
Not long afterwards support for git was added.  And then we have this:

  https://bitbucket.org/blog/sunsetting-mercurial-support-in-bitbucket

Nicely commented on by this:

  https://www.theregister.com/2019/08/21/bitbucket_mercurial_repositories/

As of 2020-08-26 (according to the first link above):

> All hg repos have now been disabled and cannot be accessed.

Therefore, since Bitbucket is now git only, go ahead and add a new mirror
source option to easily clone from a specified user and project on Bitbucket.

And, at the same time, update the labels for Gitlab to "User" and "Project"
instead of the incorrect leftover old labels from the Gitorious conversion.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>