Update of SBMLDocuments on file changes (reload new version)

[matthiaskoenig]

There should be a concept/method of updating SBMLDocuments with keeping the layout information/Cytoscape information.
Part of the solution is the current layout export/import, but there should be a default method to update models from revision to revision.
This could also integrate with #110 .
An essential part of model development is a rapid iteration of model versions. This should be supported.
A solution could be to base a model on another model, i.e. if models with high similarity (based on model differences) are found in the Network2Document mapper they should be suggested as input.
When a core model is selected information is transferred as far as possible based on node_id mapping, i.e.

• layout
• background elements and annotations
• visual style

Differences could be highlighted.

[matthiaskoenig]

No model iteration information displayed.
But the source files should be monitored and a reload offered on observed changes.