undo / redo for position/rotation/scale only as v1

[kfarr]

As a user I wish to undo past actions and redo those once undone. It's ok to have a limit of undo actions such as 20 deep.

It's also ok to start with just 1 action, such as position/rotation/scale

[vincentfretin]

I have some notes about how to implement an undo feature with the Command Design Pattern in c-frame/aframe-editor#2

[vincentfretin]

PR #676