User could specify graph vertices coordinate in graph configuration source class.
This coordinates is stored in GraphModel.
This Coordinates are logical. They being translated to JavaFx position (layoutX and layoutY property of
javaFx Nodes) during graph visualization.
If user coordinates is defined for particular node, AutoLayout should skip this node and not change
it's coordinates
Otherwise if user coordinate is not defined in graph source, AutoLayout could take place and initialize
coordinates.