Speedup Hit-in-Track, HitPattern and MultiTrackSelector

Modified the storage of hit-reference in a track into a simple pair of integers (and a RefCore)
fully backward compatible interface, including iorule.
Speedup MultiTrackSelector removing all overheads not due to MVA.
Part of the improvements are in HitPattern (more can be done, volunteers welcome)

Purely technical mods.
no regression expected.
no regression observed.
So most probably this is a bug (in all 4 lines!). It is there since ever.
cannot be tested as never executed.
I agree that if it ever to be executed it needs to be optimized.
I do not have time to fix it.
I propose to take note and go on...