Pantheon Greeter should offer assistance if an user has an invalid .Xauthority/.ICEauthority file

Most login loops are caused by people running something as root and the mentioned files getting owned by root.

Pantheon greeter should detect if this is the case and directly display a help window. The content of the help window should contain information what went wrong that and can optionally offer to resolve the problem (e.g. fixing the ownership of the files).

The problem with automatic resolving the problem is that we need to find a good way to get temporary su privileges, so if anyone has an idea how to do this, feel free to comment.

Launchpad Details: [#LP1509474](https://bugs.launchpad.net/bugs/1509474) Raphael Isemann - 2015-10-23 18:48:12 +0000