Changes to split party implementation

- Supports playing arbitrary sound along with the split (rather than just teleport sound or no sound)
- Correctly imported from older save files
- Support for splitting off an arbitrary subgroup of the party rather than just a single PC (though the special node doesn't yet allow this)
- Support for leaving town while split - if you leave town, the absent PC's items are not dropped on the ground when later entering a town
- Option to not change location when reuniting
- If you reunite in a different town than you started, you are returned to the town you split from

rsrc/strings/specials-text-town.txt

@@ -377,7 +377,7 @@ Unused
 X coordinate to place lone PC at
 Y coordinate to place lone PC at
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-0 - no telep. noise, 1 - play telep. noise
+Sound to play (10 = teleport)
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 Special to Jump To
@@ -390,10 +390,10 @@ Second part of message
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-0 - no sound, 1 - teleport sound
-Unused
+Sound to play (10 = teleport)
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+If 1, don't change location
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 Special to Jump To