Rename canvas files to viewport.

In the future, Canvas will refer to 2D view and Viewport to 3D.
Disable huge gigantic chunks of code in preparation for a substantial rewrite
Scrolling with left-click
Remove superfluous includes
Draw fake inspector windows for debug
Draw points in the background of the canvas in a grid
Zoom on scroll
Inspector code now compiles again
Adding node + inspector now works.
Tighten vertical spacing in inspector
Fix ports so they're pixel-aligned with inspector edges
Enabling selection for inspector
Move all canvas related things into a canvas directory
Adding GraphScene
Making canvas a particular type of MainWindow
Reducing interconnection in new Node UI creation
Menu item to open a new Canvas window
Connection now compiles.

(segfaults immediately because signal/slot connection occurs before the
Connection is added to a scene).
Make scene connections after the item is added to a scene
Templated function to avoid repetition