0027848: Visualization - sensitivity of lines is too high

0027848: Visualization - sensitivity of lines is too high

Improved objects sorting by depth.

The sensitivity calculation for the manipulator has been changed.
Now the sensitivity of the elements of the manipulator depends on its size.

Also fixed the problem of erroneous selection of unfilled circles (SelectMgr_Frustum<N>::hasCircleOverlap() function).

Test case vselect/bugs/bug27848 added.