Adds support to better handle air alarms in sensitive areas and vents with custom settings.

Air alarms now have a new setting, breach_detection, which allows for disabling the automatic mode change when a breach occurs.

Vents now have three new settings. These are primarily for when air alarms request a mode change to ensure that custom pressure levels/checks (in terms of mapping, not set later in game)  are not lost.
external_pressure_bound_default
internal_pressure_bound_default
checks_default
Map changes relevant to the air alarm and vent update.

The engine air alarm no longer automatically turns off in the case of a breach.
The engine core vents now have defaults set, to ensure their custom pressure levels/checks are not lost in case of air alarm mode changes.
AI now handles EMP-stun like other creatures do in their life.dm file

Previously AI would be stunned indefinitely after being hit with an EMP-blast. This would prevent emergency shutters from being operated.
The stun status is now adjusted down in the Life()-proc like is done in the base living.dm, which the AI living.dm does not ..() call.
Extends the cargo shuttle conveyor by one tile

Looks nicer.
Air alarms play a sound when there is an alarm
Adds pandarsenic's approved custom cyborg

http://baystation12.net/forums/viewtopic.php?f=33&t=10641
Updates a item sprite and adds 2 approved items

http://baystation12.net/forums/viewtopic.php?f=33&t=10693
http://baystation12.net/forums/viewtopic.php?f=33&t=10678
Paths to new files are:
/obj/item/weapon/lighter/zippo/fluff/isaac_jachym
/obj/item/clothing/shoes/jackboots/fluff/kecer_eldraran
Added system for overmap building.
-metaboject with zlevel info that should be placed on sector/ship zlevel
-overmap object that represents a map zlevel
-startup hook for building the overmap
Merge pull request #5379 from PsiOmegaDelta/AIStun

AI now handles the sunned status like other creatures do in their life.dm file
Added skeleton airlock and pod garage to the listening post, tweaked the toilet area a bit.
Fixes the jackboots
Engineering outpost airlock

- Added airlock
- Removed DJ station note
- Changed pipes in derelict atmos to hidden so they run under the wall
Merge pull request #6 from Loganbacca/derelict

Engineering outpost airlock
Merged Botany and the Kitchen, added Xenoflora laboratory.
Merge branch 'derelict' of https://github.com/Zuhayr/Baystation12 into dev
Added quality of life bits and pieces to xenoflora, listening post and merged hydro.
Reduced botanist spawn count, renamed to Gardener, increased Science and Chef spawn count, added Xenobotanist alt title to Scientist.
Merge pull request #5384 from Jarcolr/custom_item

Updates a custom item sprite and adds 2 approved custom items
Merge branch 'derelict' of https://github.com/Zuhayr/Baystation12 into dev
Merge pull request #5383 from Jarcolr/custom_synthethic

Adds Pandarsenic's approved custom cyborg sprites