Use less-aggressive CSS for ltr and inline-block, and do Edge check within the extension.

This makes the CSS specific to token elements (the only ones with text in them), so that things like math that uses <mlabeledtr> or tables with width="100%" won't be adversely affected by the change to display:inline-block. Also, moves the Edge check into the extension, since there is more to do to set up a new browser category (I will handle that in MathJax.js).