Dynamic overworld palette system

The most up to date code at time of writing can be found here. This also fixes some of the problems with the below system, like broken reflections and berry trees.

If you don't want to pull from a repository, you can look at this link here, and make the changes accordingly: https://github.com/pret/pokeemerald/commit/e4530a98cb1e4a572711563b1214468b26c3d688#diff-8306bd0c8ceabc2e2ba4ca90356ee24fadffe576b7a4b4caabe755c8f5d3f419

TODO: Update this tutorial properly, explaining the changes that are made and the reasoning behind.