Sean Chalmers

Build a better tree generator and add some validator functions.

From commit messages: > This makes it easier to combine/adapt overrides > in downstream dependencies. Without this, users > would need to override everything required by nix-thunk. > In case...

This PR removes the dependency on the mega `lens` package and creates optics and friends using the `microlens` set of packages. The use of Prisms does necessitate the inclusion of...