An easier way to add maintenance tasks?

Signed-off-by: emanuele <emanuele45@gmail.com>
Tries to use a fallback (plain function) if the activity method doesn't extis (i.e. activities added via hooks)

Signed-off-by: emanuele <emanuele45@gmail.com>
Merge pull request #509 from emanuele45/extend_maintenance

An easier way to add maintenance tasks?