Move tint colors from model surfaces to block

In Minecraft, tint colors are per-block. We should change this to allow users to customize tints per block and to implement tinting for #1332, which needs the hard-coded tints that Chunky already has in the models.

Start by locating the model-surface tint definitions and the block representation in the Java code. Trace how the existing hard-coded Minecraft tints are read, then verify that tint values can be customized per block and remain available for the tinting work in issue #1332.

Written by the indexing model from the issue text.