* Cloze styling is not required in I/O notetype
* Use raw string for IO template
* Rename to notetype.css and use more specific ids
* Move internal i/o styling into runtime
Storing it in the notetype makes it difficult to make changes, and
makes it easier for the user to break.
* Fix misaligned occlusions
At larger screen sizes, the canvas was not increasing above its configured
size, so it ended up being placed top center instead of expanding to fit
the entire container area.
To resolve this, both the image and canvas are forced to the container
size, and the container is constrained to the size of the viewport,
with the same aspect ratio as the image.
Closes#2492
