Add mkShell + mkShellWithNamePrefix
This commit works within Srid's somewhat complex framework in order to add the ability to make a shell with a set of requested linters. mkShellWithNamePrefix allows adding a prefix which will change the binary name on the $PATH Useful if you want to prepend your project name to scripts, such that people can discover the utils that have been added to their shell via tab completion.
This is the worst Nix code I have ever written. It will be merged into staging and then into overengineered to reflect that. This is technical debt.