TGG-editor: import graph action combines several files to one imported
graph, improved automatic layout for several connected graph components
TGG-editor: improved efficiency of deletion of edges for larger graphs
Merge branch 'HOTFIX' of https://github.com/de-tu-berlin-tfs/Henshin-Editor.git into HOTFIX
improved dialog for exporting graphs as image files
TGGeditor - improved code structure
TGG-Editor: improved AutoLayout for several unconnected subgraphs