shell: Clock color from theme by default
shell: Spacing around control center children
lookandfeel: Use Hawaii tool buttons for logout options
lookandfeel: Use hard-coded colors for lock screen and login manager

Default background is dark so we need bright colors, the theme color scheme
might be dark as well therefore hard-coded colors are used.
lookandfeel: Replace tool button with icon button for selection screen

Fits better with the overall look.