Show message box on fatal startup error

[Breakthrough]

Description: Now that the UI is out and more or less stable, quite a few folks are using DVR-Scan entirely without a terminal. Unfortunately, this means that on any fatal startup errors - e.g. a corrupted user config file - users will see a brief flicker while the terminal window opens, and then the application will just close.

Recommendation:

On any fatal startup errors in the app, we should make an effort to show a messagebox with the error. Ideally that might include the ability to open the log folder with the log for that run, or to copy the logfile's contents to the clipboard.