Medibot updates!

Medibots have gained two new settings!

- Virus treatment: Medibots can now be configured to ignore viral
infections, even if their beaker contains the cure. This is to stop them
attempting to contain benign viruses released by a virologist.

- Stationary Mode: Medibots now can be configured to remain in place,
healing only adjacent patients. *They will not chase patients or attempt
to patrol.*
This is useful for establishing triage and recharging stations during
blob attacks.
<b>Medibots will still respond to PDA summons or AI waypoints.</b>

Medibots in Stationary Mode will have a yellow light instead of a green one. Sprites by Nienhaus!