working on something. So, this commit includes among other things...

- Improved error reporting
- Big code cleanup for more maintainable code
- Made the config module's way of detecting/starting the daemon process more reliable.
- Systray icon tooltip now contains info on backup plan status.
- Systray icon now shows up with a red warning symbol if a plan has "bad" status; more than three times the backup interval has passed since last backup.
- Introduced a new scheduling mode, Usage. Monitors how long you've been logged in since last backup was taken and suggests new backup after configured
number of hours. Made this scheduling mode the default.
- Made a new systray icon (supposed to look like a safe... you judge..).
- The progress notification thing was just ugly & annoying, removed it. Now just showing an animated icon when taking a backup.
- Added option to never ask user before starting to take a new backup.
- Bug fix, already plugged in devices didn't show up in the list for selecting external destination drive.
- Bug fix for local filesystem destination: now detects if destination folder becomes available after a mount.