UFOPedia Update and some AI tweaks to cover edge case scenarios

Big UFOPedia Update!

Updated Seeker Target Icons courtesy of Evilbob

Eliminated a janky interaction with basegame code that could result in Nightmares behaving weirdly while lurking.

Small Animation Tweaks

Patch to fixup some animation issues and some ragdoll funk

Added more AI behavior safeguards to prevent the rare occurence where an invisible unit might run away from the player

Fix for an issue that could prevent Nightmares from unburrowing when damaged while burrowed.

Minor spawning tweaks

Fix for a bug that could allow Mind Control on certain units that are normally immune to it.