Custom Project Avatar

[cstrnt]

Issue
In the new project selector it is pretty hard to tell apart the teams from each other

Solution
Allow teams to upload an image which will then be displayed in the selector

[codiini]

@cstrnt I think we can close this as the corresponding PR has been merged :)

[cstrnt]

@codiini We still don't support custom avatars yet, the PR just mentioned that we should do it :D