[#328] fixed a weird bug under Safari/W7 where the function was undefined under the me.utils namespace

I could not figure out why this is happening, but to be on the safe
path, I moved the function to me.agent as a private one.
[#381] removed further occurence/usage of the now deprecated visible flag !
Fixed various issues in the debugPanel (following these last days commits)

- Event registration using the new pointerEvent names
- event registration/usage
- add/remove itself from me.game.world when on  showing/hiding