Consider cleaning up stale branches

[Tragetaschen]

There are currently a lot of stale branches in each of the aspnet projects that clutter the list on the Github page or when listing with git branch -a. It would be great if the merged/closed/forgotten ones would vanish.

[Eilon]

I've asked folks to clear out their stale branches, so it should get a bit better today. Thanks!

[Eilon]

Cleared out a lot of branches so far, still some more to go.

[Eilon]

Closing this issue for now because we've removed most of the dead branches. I'm still working on getting folks to delete any other unneeded branches.

[Tragetaschen]

Indeed, it's starting to look well. Thanks!