window: use GtkPopovers

GNOME Calendar uses a custom GtkOverlay-based widget, witch is not necessary anymore. It should be replaced by GtkPopover.
window: queue draw on update view
build: update requirements
app: update application menu

Use only application wide actions in the menu, as stated in GNOME HIG
Migrated to use GtkBuilder files
app: remove unused view type action
time: properly set time and timezone