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
This might not be a regression, but `getContent` results in an `AuthzAPI.hasAnyRole` call, then eventually delegates to `_getFullContentProfile` which does a `_getAllRoles`, which in a sense is a super set of the former. So we can probably eliminate that `AuthzAPI.hasAnyRole` call on private content items for every `/api/content/<id>` request.