[Feature] Fallback page when server is not running

[Yoronex]

When the PP server is not running, the client will load forever. It would be nice to have a fallback page that mentions that no connection to the server could be made. We can do this by checking the call to /getPublicGeneralInfo: if this does not return a 200, PP is not running and we should draw a nice "CBC HET IS STUK!!!11!!1!!".