Rounding - different decimal places for translations, rotations

Units of translations, rotation axes and rotations angles are different. Therefore it should be possible to specify different decimal places. (The last two parameters of round_collada_numbers.py are optional; script remains backward-compatible. Problem: Units of min/max are unknown.)
See https://github.com/ros-planning/moveit_ikfast/pull/33 . Better to fix it there.