* core: NodeChunks are now stored in a ListModel inside Node
* ui: introduce SortedModelByReference
* ui: UIGraph exposes a proxy model of its graph's nodes sorted as visited by DFS (instead of another model of chunks)
* ui: added NodeChunks Component
* 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