- deprecate VisualizerInput.getSToken() since it can be calculated easyly from the SDocumentGraph
- first implementation for also serializing the SDocument in VisualizerPanel
- typo in function
also write SDocument  to object state of SingleResultPanel
test serialization of SDocument member variable of SingleResultPanel
also add the SDocument serialization test to VisualizerPanel
some fields in QueryController don't need to be serializable
store map of node IDs in order to make the map serializable
Merged 'develop'.
also use maps of IDs instead of SNodes in the segmentation change process
also serialize the SDocument of the VisualizerInput
Serialize the Salt SDocument in VisualizerInput, VisualizerPanel and SingleResultPanel.

Also make sure that all other variables of these classes are either serializable or will be (re-) created on demand