More control over the calendar status colours

would be good to have a bit more control over the calendar statuses. right now some we can delete by accident and some we cant touch at all. one of our night staff deleted Reserved thinking it was one we made, and next morning all the unpaid bookings were grey again with the old name. took us ages to work out why. let us rename them and pick the colour, stop the ones the system needs from being deleted, and maybe show which ones are built in and which are ours