Automatic Layout: Consider size of element and connection labels

* Add IAutoLayouterTapeMeasure interface to estimate size of 
  elements, connectors, and connections
* Add DiagramTapeMeasure (SWT-based implementation for diagrams) 
 * Ensures that layouted element is opened in diagram editor
 * Uses SWT GraphicsContext (GC) to estime size requirements of
   text labels

Issue-Ref: 3433
Issue-Url: https://af3-developer.fortiss.org/issues/3433



Signed-off-by: Simon Barner <barner@fortiss.org>