AC playback control scripts 

This PR contains 2 new script:

- ControlledAC.js is meant to be played on an AC. At the top of the script can be modified the URL of the models, position, orientation, scale and some other settings relative to synching all the ACs.
- ControlACs.js is meant to be played on the interface. This allows you to control each ControlledAC you have setup individually or using a master control. The controls are : Show, Hide, Play, Play in loop, Stop.

In order for this to work, the comments at the top of each script need to be read and carefully followed.