I18n fixes related to the display panel (includes printer panel fixes)

This includes the following fixes:

• Mark display setting strings as translatable (regression)
• Add context to the above strings (#393 (closed), not a regression)
• Add context to printer options (#394 (closed), not a regression)

PS: The regression probably happened due to glade not allowing translation of the libhandy widget, upstream fix for this is: https://source.puri.sm/Librem5/libhandy/merge_requests/236