Change scene drag-and-drop modifier behavior in the 2D and 3D editors

Behavior is now consistent across 2D and 3D editors.

- By default, drag-and-dropping adds the scene as a child of the selected
  node. Hold Alt when releasing the mouse to add the scene as a child
  of the root node, or Shift to add the scene as a sibling of the selected
  node.
- To choose a different node type in the 2D editor when drag-and-dropping
  a texture resource, hold Alt + Shift (instead of just Alt).
- If multiple nodes are selected, only the first one is taken into account.
  This was previously the behavior in 2D, but not in 3D (an error dialog
  appeared instead). This makes the UI more forgiving.

0 files changed, 0 insertions, 0 deletions