Initialization; Persistent, Lazy Filters

These commits introduce initialization hooks and solve the issue of filters being created on require.

The hooks were originally created to literally create the filter when it `stack-initialize` is called, but a re-implementation of filter access (prototyped by @Bruce-Connor) rendered this unnecessary.
Here we move `sx-auth-root` down to be an argument to `sx-request-build`. The rest of the hunk's diff is indentation.