RE 7248_MantidEV_show_distance_between_last_points_picked

Initial version, works if Q is in sample coordinates for
both Q and HKL.  In order for this to work for HKL when
Q is in lab coordinates we will need to get and apply
the goniometer rotation.

refs #7248
RE 7248_MantidEV_show_distance_between_last_points_picked

The getUB() method of MantidEVWorker now includes a parameter
indicating whether or not the UB should be converted to
lab coordinates.  If lab_coords is true, the goniometer
rotation matrix is obtained from the first peak in the
peaks workspace and is multiplied times UB to get a UB
in lab_coordinates.

refs #7248
Merge remote-tracking branch 'origin/feature/7248_MantidEV_show_distance_between_last_points_picked'