"Quirks mode" SVG import

[cwillisf]

Expected Behavior

Many Scratch 2.0 SVG images have incorrect bounds or offset information. The VM (or perhaps the GUI, or some other import-related module) should "fix up" such an SVG when necessary before handing it off to the renderer.

Handling the fix-up outside the renderer means that we know when to apply the fix-up (only when importing a broken SVG) and also means that an alternative renderer would not need to duplicate the fix-up code.

Actual Behavior

The VM supplies SVGs to the renderer as-is and expects the renderer to handle the "quirks mode" rendering.

Steps to Reproduce

See scratchfoundation/scratch-render#116, scratchfoundation/scratch-render#117, and scratchfoundation/scratch-render#118