Add support for Unicable / Satellite Channel Router / DIN EN 50494

Our loyal user base has kept this feature patch alive since fixes/0.24
and its been reported as being (rock) solid by multiple users which
also performed regression tests against plain-old-DVB-S setups.

Patch by Matthias Benesch
With additions by Shinck and warpme
updated by k_straussberger

Fixes #9726
Fixes #10997
Delay concurrent tunings on shared SCR bus

Patch by warpme

Fixes #12092