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.
Audio Switcher: Exhibit all audio tracks available.

The "Play > Audio" menu now includes all the embedded tracks exhibited by the source filter and the external tracks.
Improve the infinite recursion detection when parsing playlists.

The parser was sometimes too strict and rejected valid playlists.