Use higher bit-depth for texture baking

[malpas]

Texture baking currently only exports an image with 8 bit depth. This causes noticeable stepping, because there are only 256 possible values to use. Supporting a 16 bit-depth is important for using the terrain with any other tool.

Example

When you take the texture baking output of this terrain:

And try to use it in something like Blender, you get this:

It's also flipped for some reason (ExportTexture.cpp:23).

Heightmap:

[Jaysmito101]

Hey an update to this issue this feature will be included from the next release along with 32 bit export too.

[Jaysmito101]

https://github.com/Jaysmito101/TerraForge3D/commit/caf3f55d055919322302441794e3051ff6572018 Added Internal support for 8, 16 and 32 bit textures