The ability to archive or inactivate a space

We use spaces for projects and when the project is complete, we would like to move the space out of the way by putting it on its own "Archived" tab on the dashboard.

Setting the archive flag would be a space admin capability.

When the archive flag is set, it would automatically:

• change the permissions of anyone who is not an admin to view only
• cause the space to show up on the (new) "Archived" tab on the dashboard and remove it from every other tab
• default to not including the space when searching, but add "Archived Spaces" as another type of content to include on the search screen