Replace "Hide compose button while scrolling" setting with bottom padding

[connyduck]

As discussed in our contributors meeting.

Advantages:

• last element of list never obscured by action button
• less code that runs on every scroll
• less settings to worry about

Additionally:

• Added a (smaller) padding to the bottom of lists without action button, I think it looks nice if there is a bit of white space and the nav bar divider and the last list divider don't touch.
• The list of filters had no dividers, I added them.
• Recyclerviews with fixed height (Drafts, Filters, edits) now have scrollbars
• code formatted all touched xml files

closes #1563