Make the multirecipientnotification module non-hideable

[Aaron Wells]

Mahara 15.10 depends on the multirecipientnotification module for core functionality. It should be non-hideable.

This means setting the "can_be_disabled()" function on it to false.

But further than that, there can be (strange) cases where the module gets disabled in the database, which will cause the Inbox block on the standard dashboard page to error out. I think in addition to marking that "can_be_disabled()" flag, we should change the plugin loading functions so that they ignore the "disabled" flag in the database, for plugins that cannot be disabled.

[Aaron Wells (u-aaronw)]

Low priority because there's an easy workaround: un-hide the multirecipientnotification module!

[Kristina Hoeppner (kris-hoeppner)]

This was fixed along the way. The plugin cannot be hidden via the interface.