Add Windows 8.1 ID in the manifest files.
Initialize variables in the constructor.
Update res/web/default.css.

* use the shorthand property for font
* use background-color instead of background
Adding delete file hotkey and playlist context menu option.

The deletion is confirmed by the move to recycle bin dialog.

Playback goes to the next file when the command is called.
MainFrm: Immediatly jump to rtStart if the current playlist item is already loaded.