Fixes#6913.
Splits the arrival section up into sub-areas to reduce the need of crew rescue.
Makes catwalks act as plating instead of floor.
Misc. changes.
First pass on major conversion of xenomorphs to a human subspecies. Additional condensing of various redundant mob verbs.
Converted larva and diona to their own class, collapsed the rest of xenomorphs into a human species, other stuff.
Completely removed attack_alien(). Still have to reimplement some of the lost behavior for human/alien.
Reapplies lost attack_alien() functionality other than tackling/caressing.
Further alien/humanoid cleanup and xenospawn fix-ups. Also uncommented caste verbs.
Removed half-finished abilities system since species.dm handles it.
All xenomorphs functionality should be working now, other than the HUD, tackling and the xenomorph balance issues.
Added icons for xenomorph castes, moved broadcast languages into datums, removed alien_talk and robot_talk vars.
Merged with organ removal code.
Reapplied verbs to simple_animals/slimes. Updated species definitions to have appropriate organs.
Readded tackle as a human verb.
Borer changes regarding brain removal.
Working on moving the human HUD to the species datum a bit. Mixed results.
Moved Cortical Link to a language, added borer husks.
Tidied up the HUD stuff. Still need to make it rebuild properly when species is changed, but this will do for no
Compile fix, forgot the DME.
Fixed up ventcrawl, added new organ mechanics for dionaea.
Fixed up some overlooked sections causing mobs without brains to die immediately.
Fixed up plasma generation for queens, bugs with organs, force_organ issues with set_species().
Makes APCs with different cells specific types.
Replaces arrival's APC with a higher-capacity cell variant to avoid people being unable to leave due to power failure at 12:15.
The engine core now begins without oxygen but still requires cooling and everything else.
