Additionally render the canvas at a multiplier of the device pixel
ratio, so we get hidpi images for supported screens. The fixed CSS
sizing allows us to do that.

The problem was that on Edge, flexbox apparently can grow canvas
elements, whereas on Chrome/FF the canvas width/height is respected. No
problem, we can set the width/height in CSS to fix it, which
conveniently allows us to also fix the low-res-on-retina-screens problem
at the same time.

With jscodeshift thank God

Configurable SpriteSelectorItems per row (#90). Standardized spacer variable (#84). MenuBar Pass (#130)

* Standardized use of space units where appropriate
* Reversed box classes for easier readability in Inspector
* Sprite Area: removed unused info button
* SpriteSelectorItems: fixed spacing between rows. Isolated layout + component CSS, now reusable in other context. Items per row is now easily configurable
* MenuBar: refactored structure for clickable items

The inline css method gives us nothing that CSS modules can't give us. This puts the project more in line with the way www works, and makes CSS actually readable.

Using class names gives us full control of the modal styles.