Rewrite the README, update the changelog and tweak CONTRIBUTING.md

CHANGELOG.md

CONTRIBUTING.md

README.md

textures/moreores_copper_rail.png

textures/moreores_copper_rail_curved.png

textures/moreores_copper_rail_t_junction.png

textures/moreores_mithril_block.png

textures/moreores_tin_block.png