Hide permissions that are implicitly disabled by other permissions

In channel and role permissions, it is not made obvious that turning off "read messages" will render the "send messages" permission useless - it's not possible (yet) to have a channel where you can't read messages but can send them.

I suggest that when the "read messages" permission is turned off in any situation, the option for the "send messages" permission should disappear entirely, and only reappear when "read messages" is turned back on. This will make it more explicit that no reading implies no writing.