Changed all player to AGM_Core_fnc_player.

Added altimeter, shows height ASL. Decent rate (which I'm sure I am doing wrong :D). And time.
I'm guessing it would be 100% better to have an altimeter item that needs to be an assignedItem. Will cover that next.
Added an Altimeter item.

Fixed the descent rate. Keep it at per second instead of minute simply because it produces a nicer number.
Updated to the new UI image
Merge pull request #1231 from CorruptedHeart/Altimeter

Changed all player to AGM_Core_fnc_player.