Refresh option not available for some resources that are not closed projects eclipse-platform#2538

Change made since the fix to eclipse-platform#1438 unintentionally removed the "refresh" contextual menu for resources that are not projects.

With this change the "refresh" contextual menu is shown if ANY navigator selection is either (A) an open project, or (B) a non-project resource. Put another way: the 'refresh' item is NOT shown if ALL selections are closed projects.

Fixes eclipse-platform#2538

Author: DaveCarpeneto