Update file outline to be view-based

[undecoded-coder]

Goals:

• Use NSImageView for native drawing of icon images (enabling use of adaptive images)

Status: Implemented (with issues) [Updated]

Known Issues [Updated]:

• Modifying a part (namely, notifying that it was changed) causes the outline to lose selection
• Vertical scroll bars in viewports are not displayed

Working on getting this done. Layout and display is working nicely. Unfortunately, it turns out Apple has changed the way -[NSTableView reloadData] works for view-based tables/outlines (according to the docs), so that it destroys and recreates the row views on every reload, and apparently forgets about the current selection.

Since Bricksmith sends a change notification every time a part is selected (whether in the outline or the viewport), which triggers a reload of the outline view in -[LDrawDocument docChanged:], the selection is basically lost as soon as it is made, while the viewport just acts confused (there must be some sort of dependency on the outline view selection somewhere).

[undecoded-coder]

I now have selection and reloading working together properly in my view-based-file-outline branch! It turned out to be pretty simple in the end. However I accidentally messed up the viewport layout in interface builder such that vertical scrollbars (and placard icons) are no longer displaying, so I am still trying to resolve that before I submit a PR to close this issue. Edit: This has been resolved in the submitted PR.