Added support for m3u8 links and URLs containing a file name followed by a video file extension but not necessarily ending with it.

See commit 6f83d89 for details.

Updated Regex, added limited multiple URL support (limited functionality due to PotPlayer's command-line switch and content input limitations).

See commit note for details on limitations: 1291f09

EDIT: Now includes the minor change from commit 06084aa too.

Modified behaviour of application as per user request.

Now if PotPlayer is already running, any (further) links copied will be appended at the bottom of the playlist.
Note to self: Need to do this more elegantly by detecting current playback state.