UI improvements

[mhdostal]

Apollo: Swift - Toolkit UI styling improvements #569

Adjust padding and spacing around title, input header/footer, and indent group sub-elements, including:

• [x] Title should match Popup title. The Popup title is bold; Form title looks bigger, but not bold; title is very close to top of form
• [x] Add divider below Title area. The Popup title has a divider below it; Forms does not
• [x] Ensure Form Group Title matches Popup Element title, as both are collapsable - they already match
• [x] Should not show space for a footer if there isn't one - diminished padding a bit to make this look better
• [x] Popup "groups"/elements content are indented; indent GroupElement sub-elements

[mhdostal]

Thanks!