Rename LARA_DRAW_TYPE to LARA_TYPE as it's used in more than just drawing code. Make WEATHER_TYPE a scoped enum (would have done this for LARA_TYPE too but didn't want to pepper casts in other parts of the codebase). Relabel constants in both enums.
Add kLaraTypes and kWeatherTypes and add them as tables in GameFlow.
Remove Background member - it's not level-specific so GameFlow is a better home for it.
Add (incomplete for now) documentation for some GameScriptLevel members - those I tested, at any rate.
Treat functions as global that would previously be accessed through the GameFlow table. This does pollute the global environment in Lua a bit, but keeps it consistent with the functions in GameLogicScript, which are all accessed as globals.
Add some default member initialisers.
Remove WriteDefaults. Rename Intro to IntroImagePath and make it a std::string.
Add some documentation for the functions of GameFlowScript.
Fix some comments.
