Inspector improvements

[tferr]

The SciView Inspector is really neat! but now that I've been playing around with it a bit more I miss some functionality/improvements. Some of these are really minor issues, I am just adding them here for reference.

• [x] A contextual menu to access most common commands (Delete, Show/Hide, etc.).
• [x] Since double-clicking on a node centers the view on it, I find distracting that the JTree auto-expands the node children. I would disable that (or provide an option to do so)
• [x] When a node is selected, its label becomes unreadable with the GTK L&F. It does not happen with the default Swing L&F. Interestingly, this does not happen with PointLight labels. Snapshot:
• [x] A reset/rebuild/wipe scene command (#214)
• [ ] It would be great if one could assign a common property (e.g., color, scale) to a group of nodes. I guess a way to do achieve this would be to allow nodes to be merged?
• [ ] Is it possible to have multiple scenes? If not I would probably hide the "Scene" root from the JTree.
• [ ] This is a Scijava widget limitation: Currently if one has a node with multiple children (all with the same colour) the colour widget will just render a default, unrelated color, which can be a bit confusing. A way to make the widget more user-friendly would be to find a way to render a "null" colour (e.g., the button background, a fully transparent colour) or something equivalent
• [ ] Also somewhat related, it would be nice if Menu commands would list there shortcuts

@kephale, Let me know what you think of those. If you point me to the code, I could probably submit a PR on some of this.

[kephale]

I'm going to remove the 1.0.0 label from this meta issue because I'm not sure we'll realistically get these in unless someone else picks them up.

• we are pursuing the ability to run a command on a node and its children: https://github.com/scenerygraphics/sciview/issues/241

The other ones are not being actively worked on to my knowledge.