Fix Maps Missing Assistants (#838)

# Description

Glacier, Core, and Saltern were missing their assistant job slots(My
mistake, when the Linter said I needed to set the Overflow job, I
assumed it meant "Replace the [-1, -1] slot with the Overflow", but
apparently both are needed.

Additionally, Glacier, Core, and Saltern are now added to the Map Pool.

:cl:
- add: Glacier, Core, and Saltern now have assistant job slots.
- add: Glacier, Core, and Saltern are now able to be voted on for map
selection.

Resources/Prototypes/Maps/Pools/default.yml

@@ -5,10 +5,12 @@
   - Asterisk
   - Core
   - Edge
+  - Glacier
   - Hammurabi
   - Lighthouse
   - Pebble
+  - Saltern
   - Shoukou
+  - Submarine
   - Tortuga
   - TheHive
-  - Submarine

Resources/Prototypes/Maps/core.yml

@@ -64,3 +64,4 @@
             Musician: [ 1, 3 ]
             Boxer: [ 2, 4 ]
             Reporter: [ 2, 4 ]
+            Passenger: [ -1, -1 ]

Resources/Prototypes/Maps/glacier.yml

@@ -21,6 +21,7 @@
         overflowJobs:
           - Passenger
         availableJobs:
+          Passenger: [ -1, -1 ]
           Captain: [ 1, 1 ]
         #service
           HeadOfPersonnel: [ 1, 1 ]

Resources/Prototypes/Maps/saltern.yml

@@ -62,4 +62,5 @@
             Clown: [ 1, 1 ]
             Mime: [ 1, 1 ]
             Musician: [ 1, 2 ]
+            Passenger: [ -1, -1 ]