Initial draft of profile metadata format & CLI (#17)

* Initial draft of profile metadata format

* Remove records, add Clippy to Nix, fix Clippy error

* Work on profile definition

* BREAKING: Make global settings consistent with profile settings

* Add builder methods & format

* Integrate launching with profiles

* Add profile loading

* Launching via profile, API tweaks, and yak shaving

* Incremental update, committing everything due to personal system maintainance

* Prepare for review cycle

* Remove reminents of experimental work

* CLI: allow people to override the non-empty directory check

* Fix mistake in previous commit

* Handle trailing whitespace and newlines in prompts

* Revamp prompt to use dialoguer and support defaults

* Make requested changes

shell.nix

@@ -2,6 +2,7 @@
 
 pkgs.mkShell {
   buildInputs = with pkgs; [
-    rustc cargo openssl pkg-config
+    rustc cargo clippy openssl pkg-config
+    gtk4 gdk-pixbuf atk webkitgtk
   ];
 }