Move UI functionality out into eca_ui submodule
Problem/Motivation
ECA in productions works perfectly fine without a modeller already. But it still comes with a few UI functions like the model list, the import function and so on. All of which is not required and should be moved out into eca_ui, just like views_ui and field_ui does it as well.
This was first brought up in #3275457: Error handling inconsistent when saving models and the question was if this should still be done for the 1.0 release. I do think that's important and the impact should be minimal.
Edited by drupalbot