Adding isManager/isViewer properties to content and discussion items

Added the following properties to content and discussion profiles:

 * isManager   - for when the user has explicit access to the object
 * isViewer (= isMember for discussions)
 * canManage
 * canShare

Discussions also have:
 * canView
 * canPost

Includes the follow-up for https://github.com/oaeproject/Hilary/pull/856
In `canManage`, there is a `getContent` call which does a `AuthzAPI.hasAnyRole` which is never sufficient to determine if a user can manage. So we can probably ditch the `AuthzAPI.hasAnyRole` entirely in place of a simple `_getContent` that doesn't do a permission check, and only rely on the `hasRole` check when necessary