tmf: open files without trace type with eclipse default editors

tmf: open files without trace type with eclipse default editors

Also, the navigator content label was changed to delegate the
icon selection for files without trace types to the platform.

This allows users to double-click on any file and it will open with
either as a trace type or as a file in the default editor.

Change-Id: I362dd31c4394bb00fea8ff33bc4843f799ffb3de
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/31134
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Hudson CI
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>