WIP: Handle connection issues e.g. timeout, webexception

- [x] Catch exceptions
- [x] Blank RELEASES should not result in explosions
- [ ] Log timeout/webexception/etc as they occur (BitsManager doesn't take the application name though -- how to log then? Thinking of moving `Catch`es to UpdateManager but this would mean all users of DownloadUrl would need to handle catching)
- [x] Tests