* Implement parallel scanning and generation, and combined scanning/preview/sprite generation.
* Added UI component for preview/sprite generation during scan, and configurable number of parallel tasks.
* Add v050 changelog entry
Fixed annoyingly noisy transcoding progress log messages.
Fixed minor minor issue with directories than are named "blah.mp4" being detected as files to be scanned.
* Added preview generation fallback feature.
When a preview generation fails (often for wmv/avi files), the new code tries with less stricted (no xerror) and more time consuming options (slow+fast seek).
Fix a minor issue when stash downloads ffmpeg/ffprobe, but doesn't re-detect their paths.
