Add missing grayscale conversions

Spread flakes out over 5 layers now (far back, mid distance, just behind land, just in front of lands and hog, near distance). Spread clouds out over 3 layers (far back, mid distance, just behind land). Add a flatten clouds option, use d on Underwater. Alter some flake PNGs to reduce variation in size since scaling is being used.

engine interaction class refactoring, round 4 or 5, can't remember: this time use the class methods to create an instance object and operates on that, reducing the number of arguments between methods and simplifying memory management

move two class files in a correct directory

exclude hogs from density check

too game breaking I think

Include density in gear kick

not sure why this condition wasn't here before

Due to the small values and friction, halve the step in low gravity, instead of the value

Don't set moving if on flat surface

skip when attacking as well

This has bugged me for a while. Fix text position in frame 4. Also shrink size.

A bit less WTF of ice, ice chutes now work. Also tweak flake respawn positions a bit

Some improvements to the parser

Increase rarity of near flakes (don't want them intruding in game much). Also fix stereo. Near flakes were being drawn far.

Flatten flakes for halloween theme, based on feedback from sheepluva