Enable adjusting the default permissions for a room

In our settings for circles / groups / galleries, we allow an admin user to change the power level for another user.

But not every user will have a specific power level set in the room. In fact, unless an admin specifically sets a power level for someone, they will have the default power level for the room. We do not offer any way for the admin to change this default power level. For example, maybe the owner wants to disallow posts by other users.

Proposed solution

In the circle / group / gallery settings, we should add a control to set the default power level in the room, using the same numbers and names that we use for individual users. e.g. "Can View", "Can Post", etc.