Make Teiid navigator content dependent on getting Teiid Instance

* The teiid content displayed in the Server View is determined by the
  navigatorContent extension point. It has been a permanent feature on
  install of Teiid whether the JBoss server supports teiid or not.

* Make the teiid content dependent on whether the IServer can be adapted
  to an ITeiidServer instance. This calls the TeiidServerAdapter which
  examines a running server for a teiid subsystem.

* Result is that the Teiid node should vanish for non-teiid jboss servers
  when started and remain for teiid-supported jboss servers.