Created the qsr class
Implementation of the following qsr: right, left, in front and behind.
Added the distance function.
Given a set of annotated objects, the QSR values of right, left, front and behind are showned in the terminal whenever the QSR values menu is clicked.
Merge branch 'QSR' of https://github.com/adria-gallart/3d_annotation_tool into QSR