ShareDialog: Make "can edit" partially checked sometimes #5642

ShareDialog: Make "can edit" partially checked sometimes #5642

Previously the check box was checked if *any* of its sub-permissions
were granted. This can hide the fact that only a limited subset of them
are actually granted.

The new behavior is to display as "partially checked" if only some
of the sub-permissions are available. Clicking the check box itself
still toggles between granting all or none of them.