* extract UIGraph from Reconstruction: base class that wraps a core.Graph, without knowledge of photogrammetry pipeline
* ChunksMonitor: watch NodeChunks status files for external changes to keep UI updated even when the graph is being computed externally
* Reconstruction inherits UIGraph with photogrammetry specific features
* ImageGallery displays images from CameraInit.viewpoints
* support drag&drop of images
* Viewer2D displays and allows basic manipulation of currently selected image
First functional UI that allows to visualize, modify and execute a graph locally.
* use QtQuick Controls 2 + Shapes (Qt >=5.10)
* main menu to save/load a graph