I don't see a reason why this restriction to have the selection be always
visible was necessary. Removing it has two benefits:
1. Scrolling a list view doesn't change the selection. A common scenario: you
look at one of the commits of your current branch; you want to see the how
many'th commit this is, but the beginning of the branch is scrolled off the
bottom of the commits panel. You scroll down to find the beginning of your
branch, but this changes the selection and shows a different commit now - not
what you want.
2. It is possible to scroll a panel that is not the current one without changing
the focus to it. That's how windows in other GUIs usually behave.
This begins a big refactor of moving more code out of the Gui struct into contexts, controllers, and helpers. We also move some code into structs in the
gui package purely for the sake of better encapsulation
