Poster fixes

Fixes #7261
Fixes placed posters being visible on both sides of the wall.
Fixes the poster_type var used to specify certain poster designs on the
map not working correctly, and makes the nuke op shuttle poster an
actual poster.
Poster placement now belongs to the poster object instead of turf/simulated/
Posters can now be placed on unsimulated and shuttle walls.
Fixes #7308.

Adds missing parent call in Del().
Fixes #7277, map adjustments

Fixes #7277, and includes some map changes and fixes from PR #7249.
Adds image for cult talismans

So they aren't blank when examined.
Fix for #6649.
Fix for #7330.
Merge remote-tracking branch 'upstream/dev-freeze' into dev-freeze-map
Merge remote-tracking branch 'upstream/dev-freeze' into poster

Conflicts:
	code/game/objects/effects/decals/contraband.dm
Merge pull request #7329 from mwerezak/talisman

Adds image for cult talismans
Fix for #7324.
Merge pull request #7328 from mwerezak/dev-freeze-map

Fixes #7277, map adjustments
Merge pull request #7276 from mwerezak/poster

Poster fixes
Merge pull request #7309 from PsiOmegaDelta/DiscoIsDead

Fixes #7308.
Merge pull request #7332 from Segrain/master

Bugfixes.
Merge remote-tracking branch 'upstream/master' into dev-freeze
Merge pull request #7334 from PsiOmegaDelta/dev-freeze

Dev freeze