[MadMax3947]

Variety of changes and modernization; intended to be last version for 1.19.x, and hopefully be released on 1.20.x add-on server when it comes out.

Most notable changes:

• Missing storyline graphics have been added.
• Scenario 6B (The Crypt of the Mountains): New player vision restriction mechanic.
• Scenario 7A (The Open Ocean): New dynamic lightning storm mechanic.
• Scenario 15 (Gate of Storms): Extensive additions including gameplay changes and visual/ambient effects.
• Dialogue and graphical additions and changes.
• Lua refactoring, modernization, and documentation. The dungeon generator in scenario 11B (Sol'kan's Lair) has been separated into a dungeonmapgen module, and the cloud simulation from scenario 7A (The Open Ocean) is included in a cloudsim module. Hopefully they can be put to use in others' Wesnoth content!
• Bug fixes,