Change the meson option from face to face-detection.
To compile with face support use -Dface-detection=true.
Many files used old Yorba Copyright notice, they were updated.
A class from file src/editing_tools/EditingTools.vala was moved to it own file
A bug made the menu label to be always in plural "Remove .. photos" instead of
"Remove ... photo". Now it is corrected.
The deprecateds Gtk.HBox and Gtk.Button.from_stock() where changed to they