Move swap views towards MVC

The swap code was originally conceived as being split up into something like Model-View-Controller based on the model laid out in https://medium.com/square-corner-blog/advocating-against-android-fragments-81fd0b462c97 But the existing implementation mixes up all three components quite a bit. This merge request is a big step towards making the View actually really only the View. The goal is to make as many Views as possible purely implemented in XML, that will draw a very clean line keeping Model/Controller code out, since that can't be done in XML. There will probably still need to be 1 or 2 custom View subclasses, since there are a couple quite complicated Views.

That said, this merge request still leaves lots of Model/Controller code in the Views. I'm working on that. But now it is at least much clearer to see which code needs to be moved out of the Views.

@Bubu you were interested in the past...