VDR Block Plugin

New Features:
-The main menu entry now not only adds the title of the current
show to the blacklist, but also permanentely removes the title
if it is already found in the blacklist.

Bugfixes:
-with detection method set to 'Channel EPG' and replay of recorded
shows was terminated on block event on the underlying channel.
Fixed now.

-Channel Up and Channel Down keys were not working at all! Different
from VDRs key handling of Up and Down the Channel variants were eaten
by VDR itself and made it ignore the plugin code (however the plugin
correctly detected the keys...). Fixed now by kind of a workaround.
Thanks to igel for reporting this bug.