Restructure crates

Get rid of the arbitrary bin/lib split and instead move as much as
possible into the bin crate, which becomes the main crate again.

The types and NBT handling are moved into separate crates, so they can
be reused by nbtdump and regiondump.

src/main.rs

@@ -0,0 +1,19 @@
+//! The minedmap generator renders map tile images from Minecraft save data
+
+#![warn(missing_docs)]
+#![warn(clippy::missing_docs_in_private_items)]
+
+mod core;
+mod io;
+mod resource;
+mod util;
+mod world;
+
+use minedmap_nbt as nbt;
+use minedmap_types as types;
+
+use anyhow::Result;
+
+fn main() -> Result<()> {
+	core::cli()
+}