Simplify api to move the head with a single name

[ntorresalberto]

There are 3 functions that seem to handle the same use case (moving the head) but differ in naming (these are all in head.py), making it confusing for the end-user even though they change input arguments:

• rotate_to handles RPY parameters,
• orient takes a quaternion
• look_at takes an XYZ from a point in space

To simplify it, I'd suggest sticking with a single root for at least 2 of them (not sure if it's possible for look_at too): rotate_rpy, rotate_quat. There might be an alternative to rotate that could work with look_at. That'd be great.

[ClaireHzl]

Had been modified into goto (handles rpy parameters and quaternion) and look_at