new method to return entry contents without user-disabled objects

We can’t globally make the change in scannedObjects or
contentsScanIfNeeded:, because there are places where the objects
should still appear. For one, they should appear in the prefs so you
can re-enable them.
prevent user-disabled objects from appearing in the UI

fixes #1685
Merge branch 'master' into omitted
Merge pull request #1688 from quicksilver/omitted

Prevent user-disabled objects from appearing