Major guide snapping improvements
- Snap lines doesn't show up for 'node' files. (Created with File > New > File... > Node)
- Grid should fill the screen, not only the content area.
- Edges and corners doesn't snap to guides.
- Holding down cmd still snaps to guides and grid.
- Horizontal position marker on the ruler is incorrectly colored.
- Snapping lines appear when scrolling the main area and an object is selected