* expose node types model as context property
* right clicking on an empty space inside the Graph Editor opens Node Creation menu with all available node types
* add WorkspaceView that contains Meshroom main modules (ImageGallery, 2D/3D viewer)
* add Panel component to standardize UI modules layout
* ImageGallery:
* add images basename on image delegates
* add explanatory placeholder when no image has been added to the reconstruction yet
* add Rotation/Scale controls
* add controls to disable default items (grid/locator)
* add drop support to load external 3D models
* add "View All" action in contextual menu to fit to scene
* automatically propose to load the reconstructed mesh when available
* add button to submit the graph to the default submitter
* add warning message when the graph is being computed in another meshroom instance
* make Start button green
* setting readOnly to 'true' disable editing on AttributeItemDelegate components
* use this property instead of disabling the whole AttributeEditor when graph is being computed
* 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
