Externalizing strategic map secrets

[ja2-derek]

This PR externalizes (#665) map secrets to JSON data files. Map secrets in base game are: Tixa, Orta and the 4 SAM sites. They are hidden at the start of game, and revealed to the player by NPCs or when arriving at the sectors.

Summary

• Moving the traversibility mapping (from string name to enum ID) to its own file
• Extracting map secrets information from code:
  • Sector (as primary key); Map icon; Terrain land type string
• Refactoring the sector description function (e.g. "Cambria Hospital", "Tixa Dungeon", "Farm, road")
  • Using the newly externalized data to determine land type for secret sectors
• Generalizing map secrets and save games:
  • fFoundTixa is generalized as "1st non-SAM site secret"
  • fFoundOrta is generalized as "2nd non-SAM site secret"
  • SAM site secrets are now dynamically defined by JSON, so that a mod can have any number of hidden SAM sites
  • NPC actions and quests still have direct references to TIXA and ORTA

Limitations and assumptions

• The "is secret found?" state of only the first 2 secrets and SAM sites are saved - to fit fFoundTixa and fFoundOrta. A mod can define more but state persistence will not handled by the base game.
  • Some possibilities are: changing field from BOOLEAN to bitset, or allowing Lua scripts to write extra data to saves.
• There is at most one secret per sector
• A secret town can only have 1 town sector

Possible use-cases

These should be feasible, but not tested. Testing was done with vanilla data

• Replacing map secrets with other secret facilities on the map, and with new icons
• SAM sites that are known on game start (SAM sites without corresponding secret)
• Hide Estoni, until some NPC tells you about it
• Make the random weapon cache a map secret - that can be revealed by quests or NPCs
• Enabling PATCH106

Testing

• Save/load of secret revealed states (Tixa, Orta and SAM sites)
• Revealing of secrets by NPC
• Revealing of secrets by visiting
• Sector string in bottom-right, saves and strategic map pop-up

[selaux]

LGTM. Thanks.