now $DISPLAY is used instead of :0.0

this way, there will be a keyframe every 150 frames

Lossless may save computing power.

The Skript now uses a timestamp and a counter as filename.
You can also enter an optional prefix.

The other Screencap skripts where been deleted, so we only have one, which works.

Signed-off-by: Lars Beckers <lars.beckers@rwth-aachen.de>