Alllow for multiple modes of object placing

[gstavrinos]

Currently the user specifies only x,y and the rest are calculated by the planner, assuming that the object must be placed on the same surface it was picked up from, maintaining its pitch and roll.

Other useful modes:

• The user can also specify a z value, without caring about the object's rotation.
• The user can specify a quaternion, which indicates the object's rotation.