Implement correct pre/post poses in tool frame pose

[GreatAlexander]

Currently we assume only top-down manipulation, thus pre/post grasp is the same: Z += 0.1
We need to calculate it in the tool frame pose.

[23pointsNorth]

Maybe we can specify it somehow from here - https://github.com/ipab-rad/rad_pr2_stack/blob/dev/pr2_picknplace/src/pick_place.cpp#L364 just expand the move group joint model?