UAVs - Add Pilot Camera/Sane Solo Use Capability

[LorenLuke]

Ultra-lightweight reimagining of #7485.

When merged this pull request will:

• Add pilot cameras to vanilla UAVs.
• Provide additional UI to UAV usage, including horizontal compass
• Slave UAV turret and designator to tracked pilot camera point when locked (Ctrl+T), as long as its gunner position is not occupied by a player.

Known Issues:

• UAV Pilot camera shares the same location with the regular internal camera, meaning the UAV body obscures the view when looking backwards. (Solution unknown at this time)

[LorenLuke]

Requesting Review.

[LinkIsGrim]

Testing looks good but I'm really worried about breaking things with this.