AGM_Interaction: Name tags for units around the center of screen

* Added alternative mode for displaying names and ranks; it shows for all nearby units that are near the center of the screen (not only cursorTarget). The nametags fade as you look away or increase distance. Works better than default mode when freelooking (cursorTarget doen't follow head unless you are moving).
* There's an AGM_Option to switch between the default mode and this new one (default is the old one).
* For both modes, introduced a height offset for the icon based on distance, to allow longer visualization ranges without text osbcuring the player.
* For both modes, replaced the color of non-group units for vanilla A3 orange. Close  #670
* For both modes, introduced an AGM_Parameter controlling the max alpha of the nametags

Video:
https://www.youtube.com/watch?v=d4nPToDJeIs