Handle startup issues

The problem is that the possible exceptions from WindowsFormsApplicationBase.Run are not documented.
If we implemented single instance management ourselves, we would have to deal with the same issues, we would jest be able to catch specific exceptions. Maybe the Microsoft's intention was to wrap all exceptions in CantStartSingleInstanceException, but apparently it doesn't work.
All in all, I think this solution is good enough.

As to the network connectivity requirement - it just requires localhost connectivity, so it's ok.

Fixes #280.