Convert control map to new format

[TokisanGames]

C++

• Converts old RGB8 control maps to new 32-bit integer (stored as RF) format
• Editor changed to write this format
• Automatically generates default noise texture if blank

GDScript

• Hide opacity for paint texture
• Change tooltip names
• Improve handling of mouse clicks and edit operations

Shader

• Changed to read the new format
• Weights are separated out from material function
• More documentation and clarity
• Adds option for alpha blending instead of height
• Adds blend sharpness
• Adds slot for noise texture, which is used for blending
• Debug shaders now has two for Control map. Control texture shows base/overlay textures as red/green brightness is index 0-32. Control blend shows greyscale blend value. Good for viewing the blend noise.

Fixes #115