Use prettyconf instead separated settings files

[raelmax]

I think use environment variables it's a better way to separate development and production settings and the prettyconf project can be useful in this implementation. I can do this improvement, what you think?

[hersonls]

@raelmax it will be awesome!

I believe the default settings for frontend paths, like static and templates can come from frontend app ( which will be a external package soon ).

So, if you need to set default values for these settings backend/backend/settings/develop.py#L3-L24, lets think about move the default values to backend/apps/frontend, some conf.py file for example.