Massive change of API

[edisonywh]

• Better handling of associations (still a bit to be desired)

• Massive change of API, moved from a single Backoffice.Resources module that users have to use to two separate Backoffice.Resource.Index and Backoffice.Resource.Edit. Not sure if this is exactly the best idea, but I wanted a better UI to show associations (especially has_many), and the ideal scenario was a table/index view near the bottom of the edit page, but with the existing pop-up modal this is not really feasible. So as part of that change, I decided to break them to two separate modules.

[edisonywh]

I'm not sure if this is the best way since users now need to duplicate implementation for Index and Single.

Maybe one way to help is allow users to "tie" a "Single" module to a Index? For example something like this:

defmodule YourApp.Resource.Single do
  use Backoffice.Resource.Single,
    parent: YourApp.Resource.Index
end

This way it communicates the relationship between Single & Index, and also mean that user don't need to redefine all the resource opts. Not sure where to go from here.