Port to libadwaita 1.4 and AdwBreakpoint
This MR gives us a much simpler UI file, greatly reduced code volume, and better behavior with regards to aspect ratios. Now the clock switches to portrait layout whenever the window has a portrait aspect ratio, or if it is too narrow to fit the clocks in landscape.
Closes #25 (closed) and #21 (closed).
Edited by Clara Hobbs