Proposal: Allow pyro DSL outside resource

[frankdugan3]

Is your proposal related to a problem? Please describe.

It is not a great model to always require UI definition inside the resource config.

Describe the solution you'd like

It would be ideal if pyro DSL could be used both inside a resource, or separately. This would allow:

• Better architecture through separation of concerns
• Multiple UI's to be built for the same resource(s)
• Higher-level features, like nav_bars, which encompass multiple resources

Express the proposal either with a change to resource syntax, or with a change to the pyro interface

For example

pyro do
  resource MyApp.Resouce
end

Additional context

A possible implementation of the first parts of this idea:

1. Add a resource option to the root pyro DSL
2. Store __MODULE__ as the default value
3. Add validation to the transformer to check if the resource module is actually a resource
4. Add calls to Code.ensure_compiled(resource) to allow for the required introspection.
5. Refactor transformers/validators to correctly reference the configured resource module instead of the DSL directly.