Add support for color tinting (e.g. grass color)

[DragonDev1906]

Overviewer is doing this in the C-code and checks for a list of blocks. Maybe we should give it a list of IDs that should use color tinting. Alternatively we could have a data value for every biome.

[DragonDev1906]

The following parts need changes:

• [X] Shaders need to be able to render all non colortinted faces black so other code can add the color tinted faces later b5f64d32ad6faeb9802aa02bc06d6b1cb62df0c6
• [X] BlockRenderer needs to use the shader option to render the colortint template (this is done by returning the additional Image in the variants tuple as the second entry b5f64d32ad6faeb9802aa02bc06d6b1cb62df0c6
• [ ] Change the Textures- and C-code to use the additional Image (probably requires a get_colortint_texture(blockid, data) method in Textures)