* keep track of currently hovered node in UIGraph on Python side
* Node: show border on hover + make MouseArea contain everything else to always get hover events, even when cursor is over children attribute pins
* make Drag/DropArea overflow on the attribute's label to be more tolerant when connecting attributes
* add visual feedback when hovering interactive areas
* tweak spacings between attributes
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
* bugfix: in latest PySide2 versions, application palette is not properly applied to all QtQuick Controls 2 components. Force this by exposing QApplication palette and bind it to the root ApplicationWindow.
* rename all "palette" ids to "activePalette" to avoid clashes with "palette" property on QtQuick Controls 2
* use parent component palette when it makes sense to propagate active/disabled style (instead of always using Active SystemPalette)
* allow duplication of one node/all nodes following a node
* actions available from Node contextual menu and Alt+Click on node for multi-nodes duplication
