Refactor Library

The launcher code was in a position ripe for sphagetti, so this rewrites it in a more robust way.
In addition to cleaner code, this provides the following changes:
- Removal of obsolete Mojang authentication
- The rebasing of some internal state into a Sled database
- Tweaks which make some internal mechanisms more robust (e.g. profiles which fail to load can be removed)
- Additional tooling integration such as direnv
- Distinct public API to avoid messing with too much internal code
- Unified error handling in the form of `theseus::Error` and `theseus::Result`

theseus_cli/src/main.rs

@@ -15,10 +15,12 @@ pub struct Args {
 #[tokio::main]
 async fn main() -> Result<()> {
     let args = argh::from_env::<Args>();
-    theseus::init().await?;
+    pretty_env_logger::formatted_builder()
+        .filter_module("theseus", log::LevelFilter::Info)
+        .target(pretty_env_logger::env_logger::Target::Stderr)
+        .init();
 
     args.dispatch()
         .inspect_err(|_| error!("An error has occurred!\n"))
-        .and_then(|_| async { Ok(theseus::save().await?) })
         .await
 }