Also include customization functions to easily include it in matrix
workflows. In this context amend the list of initialStep tracking
modules for MTV timing plots.

- Replace dynamic_cast on TrackerRecHit with trackerHitRTTI::isFromDet() + static_cast
- Make the offset business more clear in the layer structure building
- Reduce temporaries
- Restore exceptions

The seed-candidate hit index mismatch seems not to be occurring
anymore (at least on a test of 100k 10mu and 10k ttbar nopu+PU50+PU70
events).

The other constructors already were out-of-line, and this way the move
operations can be called everywhere without requiring the #including
the mkFit headers.

Improve content, and also move comments for better formatting

…o convertLayerNumber()

…sterChargeCutLoose'

…entation