Tracking4D: Add config file parameter to specify planes that should not be used for the track seed

Tracking4D starts out by going through the list of planes, calls the first detector with a cluster on it reference_first and the last detector with a cluster reference_last. The track finding is based on a straight line between those two.

I have a case where the very first detector plane (a timing reference placed before the Mimosa telescope) has a much worse spatial resolution than the following planes used in the tracking. After experimenting a bit, I found that the track finding is much more successful if I make sure this plane is not used as reference_first, so that the straight line reference track can be constructed from two telescope planes instead.

To steer this, I've added a parameter exclude_from_seed to the config file.

Putting this here as a merge request in case you think it can also be useful for other users.