Rename rust_crypt directory to rust-crypto and crypt-util to rust-crypto-util

This new naming is more consistent and I like it more. I recall that there used
to be some sort of bug in rustpkg where it didn't like handling the dash in the
folder name. Anyway, that seems to work fine now.
Remove the last parameter to copy_memory() since it no longer expects a length parameter
Update README.md
Add pkgid attribute
Stop using rustpkg for building and use make instead

rustpkg still seems to have some issues, most significantly it can't handle
the rust-crypto-util crate all that well - doing a rustpkg install to fetch
this project results in an error trying to build rust-crypto-util.
Rename rust-crypto-util's main.rs to tool.rs

Doing this renaming prevents rustpkg from trying to compile the tool. This
works around a bug in rustpkg install that causes errors when using rustpkg
to fetch this project from a remote location.