Allow animated pictures in special dialogs

[NQNStudios]

This adds the choice to make pictures in special dialogs animated. (Town Stairs are not included because they don't have a free node flag to match the other ones. But they could get this feature too, and if they did, anim_pict could be removed.)

I tried to change it so -2 is the magic value for an infinite anim loop but that I haven't tested that thoroughly.

Fix #146

[CelticMinstrel]

Okay, so there's a problem with this fix for #146. It's fine in the case of dialog nodes – they can now pick either a static or animated boom. But the problem is, the "Animate Fake Damage" node can now pick an animated boom, which is wrong – that node should only allow static booms. (There's a separate node, "Do sfx burst", for animated booms.)

[NQNStudios]

Ah yes. Choosing an animated boom for that node cause the game to crash.

I just tested and found that Do SFX burst isn't working... Gotta check if this PR broke it or if it was already broken.

EDIT: SFX burst is broken in master. I opened a bug for it (#644)

[NQNStudios]

I've added a restriction on Animate Fake Damage so it's static booms only.

This required modifying the special nodes dictionary behavior so it could conflict with your WIP #607 branch.

[NQNStudios]

I tested the -2 = infinite change and it works. Now the -1 default value = no animation.

[NQNStudios]

@CelticMinstrel win-vs64 will fail but this should be ready.