Adds IPC overloaders

[Jaraci]

See title. This is a huuuuuuuuge WIP, but I think I knocked out most of the really arduous coding-related stuff when I first started on this, and hopefully the rest of this will mostly be slotting more effects and possibilities into a framework that already functions. I'm picking it up again now that I'm more or less not on break anymore.

Basically:

• the dataport is a new internal organ which every IPC will now have in its head
• overloaders are little USB-stick type things that slot into an IPC's dataport
• overloaders will apply various effects to their installed mob while they are still 'active', similar to how drugs metabolise through organic mobs
• most of these effects will be low-level and flavour only (again, like reishi/space drugs/whatever), but the functionality for more mechanically-oriented overloaders for antag or admin use is there too

Everything here is placeholder and subject to change (especially the sprites, which I will probably either have to sweat hard at or find help for) but the basic skeleton is at least working. This implementation of overloaders is intended to be compliant with the synth team's depiction of them on the Konyang page -- hopefully, once it's done, it will be modular enough to allow easy addition of more, different overloaders as contributors see fit.

[Jaraci]

!wip