replace usernames mentioned in issues, pull requests and comments, with
a link pointing back to the original gitlab user. The link text makes it
clear that it points to a gitlab user and not a github user.

This occurs regardless of what's in usermap in the settings. usermap is
now only useful for assigning issues and pull requests to users.

Disable assignments altogether. The script shouldn't attempt to set
assignees on issues and pull requests. Instead, we will add them
manually.

Note that "usermap" in settings will now be completely unused.

…s-with-links

replace usernames with links

…en-MRs

only transfer open MRs: never migrate MR as issues

…lab-issues-or-merge-requests

add links back to original issue or merge request

…es-or-pull-requests

don't assign issues or PRs to anyone

don't produce any message claiming that an MR is being processed, unless
it is an open MR. (Only open MRs are processed and transferred, now)

previously, a Merge Request would not be migrated if an issue existed
with the same name. This was because Merge Requests could be migrated as
issues, and the goal was to avoid duplicates.
However, there were too many false positives.
Merge Requests are now no longer migrated as issues anyway, so this
check is being removed.

merge requests are no longer being migrated as issues under any
circumstances, so this is an uneccesary label.

…mr-transfers-earlier

Don't even attempt MR migrations unless the MR is open

Update README and sample_settings