Branch/heightmap

This provides a driver and associated component for heightmaps

@BrettASwift @kadst43 would you mind reviewing?
I believe this is the value of `[ 0, 0, 255 ]` `r = 0-255`, `g = 0-255 * 256`, `b = 0-255 * 256^2`. The full range is `r + g + b` or `255 + 255 * 256 + 255 * 256 * 256` which is: 16,777,215.