WIP: Enable VeloPixelTracking to run in extreme scenario skipping modules

In this merge, there are the patches I used to enable the PrPixelTracking to run in the extreme conditions as well as an additional flag enabling a small speed-up of the algorithm when processing all the modules concerning the treatment of 3 hit combination. Features of the algorithm:

• allow removal of modules ( flat cut in min, max )
• HardFlagging strategy , hit flagging is also applied to earlier 3 hit tracks if they pass the cut and a complete new set of doublets are used (OFF by default)
• SkipLoopSensor, apart from last modules in the velo, pairs are built skipping some module combinations ( OFF by default)
• MaxMissed is accounting for a full "station" missing, and different logic when crossing sides of the velo