* Make accents zero width
Make the width of an accented character equal to the width of the character,
by making accents zero width. In particular, fixes#1028 (`\ddot\imath`).
This involved reworking all of the accent offset machinery, in particular
skew and accent-hungarian. A bit cleaner now.
Also added support for the new width character metrics in symbolNode.
* Update AccentsText test
* Fix comment
* Use inline SVG for stretchy elements
Replace all background-images with inline SVG code.
Pros:
* `\color` works in all browsers, even IE/Edge
* Better printing
* Much simpler CSS
* No links to background-images
* No `mask`
* No browser-detection
* No external SVG files
* Faster first rendering
Cons
* No image caching
* Heavier HTML load
* Larger JavaScript file
* `\cancel` line is in `px` units, not `em` units
* Remove static/images from make file
* Change \cancel from px to em
* regenerate screenshots for functions using inline svg
Summary:
Stuff like `\red{\overbrace{AB}}` works now in addition to `\color{red}{\overbrace{AB}}`. Strikethrough now respects color. The Firefox in the screenshotter doesn't seem to support `background-image` + `mask`, but I manually tested that the latest Firefox does.
Test plan:
Ran `make`, then tested in latest Chrome and Firefox to ensure color support was working, then ran `make screenshots`.
