Custom Track Tutorial/Animations

Programs:
 * btk-conv by Yoshi2 for BTK files
 * bark-conv by Yoshi2 for BRK files
 * BTPxT by MasterF0x for BTP files

While all the above steps are mandatory for a custom course to load, animations are not. Nevertheless, animations are an easy way to add movement and excitement to a stage.

BTK / BRK Specifics
 * These files have keyframes, meaning that an animator only needs to specify values at specific, important frames.
 * Every material animation in the same file will share the same duration and loop mode
 * Tangent values define what the value will be in between the keyframes
 * For Bezier Interpolation, set the tangent at "0"
 * For linear interpolation, set the second tangent of the current keyframe and the first tangent of the next keyframe to be (next value - current value) / (next time - current time)

BTP Specifics
 * In .btp files, every frame of an animation must have a defined value
 * The values in a .btp file correspond to the order of the textures in the texheader .json file
 * Specifying "0" for a frame in the .btp file will cause the texture at the 0th index in the texheader file (the first one) to be loaded in for that frame.
 * Each material animation, even in the same file, has its own duration. There is no loop mode for .btp files.