Handle nodes move and auto-layout on Python side by using GraphLayout and MoveNodeCommand.
* Node QML component relies on underlying core.Node object's position
* MoveNodeCommand is called after a Node has been dragged
* partial/full auto-layout for specific graph operations (Duplication, Augmentation...) are now part of those operations
* serialized position in node data allows to properly restore nodes coordinates on undo/redo
* remove all layout/node moving code from QML
* move LiveSfmManager.stepCreated to Reconstruction.sfmAugmented
* add utility methods in Reconstruction to get all images/views used in the graph
* ui: perform local auto-layout on sfm augmentation on created nodes