Add modifier to translate center of the cylinder along the cylinder axis.

A new interaction state "TranslatingCenter" is added in order to offer the possibility to translate the center of the axis along the current axis. Use case: set the cylinder so it passes at one position, move the center to it, then change the rotation axis to set the second axis 'end-point'. To use this feature, the user must select the center 'sphere' representation then move the move while pressing CTRL key.