Corbicula anti virus: threaded

Today, I fiddled a bit with threads. I've managed to separate the actual virus scanning process into a worker thread, where it doesn't interfere with the responsiveness of the user interface.

Corbicula now also displays which files are being scanned and pulses the indeterminate progress bar.

I'm not happy with the way windows are created and destroyed, so that may be subject to change in the near future.

I'm reasonably happy with the user interface now, though it's far from finished, it gives a good first impression:
So much to do, and so little time to do it...