marker to marker distance calculation range

[Dave Baier]

Currently intermarker distance averages and sds are calculated from all digitized data. Ideally we could limit this calculation to the range of digitized data that is actually being used.

[Benjamin Knorlein]

fixes #32 and #29 : Intermarker distances can now be exported for a specific range. The export also adds the mean and sd for each rigid body

→ <<cset 0cd27ef6159c>>