install: only puavolocaladmins and root are allowed to call org.puavo.client.Daemon
install: fix typo
install: extract "list old images" -functionality to a separate script
install: add new translatable strings for "Update failed"
install: script for listing imageoverlays of old images
install: by default, do not delete images if they have overlays

An explicit --delete-overlays flag can be given to puavo-update-client
to allow deletion of overlays of old images.
install/applet: fix error logging
install/applet: ask confirmation to delete overlays
install/applet: update translations