Add the ability to resize CreatePanel and Outline/Inspector panels

[thachmai]

Current these panels take a fixed amount of space which limits the available real estate for the canvas.

If there is a way to resize these panels (by drag and drop a vertical bar?), it would make app much more fun in "play" mode.

I should be able to contribute a patch if the feature is approved.

[electronicwhisper]

Yes, this would be great!

Design-wise, resizing the right hand side bar should have no problems. It will scale very nicely. The left hand bar needs some design work, e.g. issue #20, but this is a separate problem.

For the implementation, I think the state (that is, the sizes of the bars) should be stored in Model/Editor. For consistency, please use the DragManager mechanism for handling the drag operation. Here is an example of it being used.

Happy to discuss further if you have questions.

Thanks!