AGI: Refactor PictureMgr, support early KQ1 pics, fix Troll fill

[sluicebox]

This PR:

• Creates PictureMgr subclasses to separate PreAGI code from AGI
• Implements KQ1-Early picture support in a new PictureMgr subclass
• Implements Troll Tale's custom flood fill, fixing the Troll
• Documents PictureMgr and friends

At some point this was about adding Apple II picture cropping. Detours were made.

While testing, I saw that the Troll from Troll's Tale was missing flood fills in some rooms, so that got reversed and bundled in. It was a good test of the new structure.

To my knowledge, this is the first public implementation of the "Game Adaptation Langage" picture format from early KQ1. I reverse engineered it last month and developed the renderer in my tools, so porting it over was another good test. Although this KQ1 code isn't directly usable (yet??) I patched scummvm to display all the pictures for screenshots and they look good. We are nowhere near supporting these KQ1 versions of course, but now there's one less obstacle.

Show thy face, Troll

Show thy shirt, Troll

Screenshots of futures past

[bluegr]

Very nice work!
Subclassing the picture manager made the code much clearer, clearly separating the changes in the different AGI versions. It's great to see that documentation on the various picture functions had been added. Glad to see progress with the early KQ1 booter version :)

Thanks! Merging