Quest system

[avaer]

Adds basic quests support to the engine.

This is handled with the new quest type that can be inlined into the scene, much like lights/rendersettings.

The concept of quests is that it's an instruction to the engine that completion of some goal should cause some action. For example, defeating a boss should drop loot.

The system is specifically designed to be generic so that anything that would fall under the umbrella of a narrative quest in an RPG or action game can be represented and given first-class consistent presentation+gamefeel using quest subtypes, even though quests are distributed UGC implemented by different authors/land holders.

Using quests to drive a scene provides other major advantages:

• It's easy to declare a gameplay/narrative loop without programming
• First class UI support for quests, to keep the game streamlined
• Minimap/pathfinding support built in
• An easy mechanism for dropping automated gameplay rewards on completion (which may or may not have any actual value)
• Quests are tracked in the quest log, allowing the player to bookmark gameplay tasks and keep track of what's happening
• Deep AI integration, so characters know how to join, help, or hinder the player in the quest