ZFinder bug fixes and option for running in jet super ROI

Added ZFinder options for jet super ROI to trigger fast track finder configuration and made some small improvements to the ZFinder code. ZFinder before fast tracking in jet super ROI can be turned on using flags.Trigger.InDetTracking.jetSuper.doZFinder=True; in --preExec options for Reco_tf.py.

It effectively reduces the ROI for FTF seeding from +-180 mm to +- 20 mm around the z-position found by the z-finder.

Two bugs in the ZFinder are fixed:

1. Spacepoint selection - an indexing bug meant that if spacepoints which don't pass the maximum layer number and ROI phi selections occured in the spacepoint vector before those that do pass the selection, zero values of phi, rho and z coordinates, and layer number, were used by the ZFinder instead of the correct values for the spacepoints. This only caused small changes to the z histograms in my tests, but sometimes resulted in the wrong z peak being selected and hence reduced tracking efficiency.
2. Vertex significance calculation - instead of adding 3 consecutive bins, it was adding the last of the 3 twice to the first bin. This was only done if MinVtxSignificance was set to a value above 0.

Tagging @lshi and @lbeemste since this affects b-jet trigger -- although the default b-jet trigger behaviour should be unchanged.