[WIP] Add an automated grey goo command

[Arch-Shaman]

Implements / fixes #2548 (didn't know this was a thing, thanks @sprunk).

This adds a command for grey goo units that will:

• When issued on a wreck the unit will move to it then consume it before performing the next command. (This is useful if that Dante wreck or whatever is in noman's land and you want to send puppies after it then go perform some other task [eg: return to base to be reclaimed])
• When issued as an area command, the unit will move to and consume all wrecks in an area (starting with nearby ones then working to the next closest one).

The goal of this pr is to automate grey goo units in a way users can set up a command and forget about the task.

TODO:

• [ ] Add custom icon (currently uses the grey state of puppy reclaim) -- Extra?
• [x] Grey goo units spawned from hosts that are performing CMD_GREYGOO inherit the cmd and add a guard order afterwards.
• [ ] Stop performing cmd when the greygoo state is toggled to off?
• [x] Add demo video.
• [ ] Better command name. "Reclaim (Grey Goo)" may be misleading?
• [x] Decide if command should require LOS of wrecks or HadSight of them. (Likely require LOS)
• [x] Alt makes persistent command.
• [ ] Potentially filter out resurrecting wrecks (non single targeted)