Standard lib in Psil

[eric-unc]

I'd like to have some code loaded after the native code. There's a lot there can be expressed directly in Psil that can't be as easily in Rust.

[eric-unc]

Part of #41.

[eric-unc]

There's a separation between "pure" and "native" now, although I honestly have no clue if it works outside of my dev environment lol.