Maroon and Destroy objectives for Traitor and Changeling

Maroon
-Maroon objectives are a variation of assassination, where preventing the escape of the person also counts as a success.
-Aprox. 30% of assasinations will be maroonings instead
-Disincentivizes players from staying behind on the station when the shuttle leaves simply because "it's more safe"

Destroy
-Basically an assasination objective where the AI is the target
-All traitors have a 1% of getting this objective. Changelings have 2% chance.
-Adds variety, counterplay between those who want to destroy the AI and save/restore/steal it
-It is entirely possible to get Destroy AI and Steal AI at the same time. While it would be difficult, it's still entirely possible to destroy your target and steal a different AI. The chances of getting both are very slim, however.
-Encourages restoring the AI over killing it wherever possible. Discourages AIs from cooperating with antagonists.

And there you go, my hamhanded attempts at some new objective types.
Can add maroon and destroy via Traitor Panel
Checks for minds before adding AIs to the list of destroy candidates
Merge pull request #4538 from Ikarrus/maroon

Maroon and Destroy objectives for Traitor and Changeling