* add inheritance edges between parents of active symbol and other visible symbols
* add dashed inheritance edges when symbols are no direct decendants
* inheritance edges are also respected in layouting, putting base/derived classes in the correct top/bottom spot now
bug id = 167
* Added TrailLayouter with Sugiyama dependency layouting
* Layouter supports horizontal and vertical layouts
* Added basic ui to graph view for showing incoming and outgoing paths
* Added depth slider, with infinity at maximum
* Disable trail ui when not available
* Added trail messages to undo stack and only use last one when undoing
* Added QtGraphLineBezier for trail graphs and refactored other line types
* Disabled edge activation for trail layouts, shown only visually
* Highlight all connected edges when hovering a node in trail layout
* Use different color when highlighting call edges for better contrast
* Fixed BucketLayouter issue when edge does not leave node
* Increased click area for angled edges
bug id = 249 337
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Eberhard Graether