backup: use simple classes instead of hashes, use events for appmenus
backup: use simple classes instead of hashes, use events for appmenus

This makes typo errors much easier to find (also using pylint or so).
While at it, also removed explicit appmenus backup, as it should be
provided by appmenus extension.

marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin