Autolinks were not being displayed as such in the editor, changed
'linkhref' to 'link' in line 72 to fix it.

Added support for GFM double bracket links. '[[link]]' is now displayed
correctly as a link by the editor.

Added coloring support for latex formulas, usage of
- "$formula$",
- "$$formula$$",
- "\( formula \)", and
- "\[ formula \]"
will now be highlighted with the same coloring used for strings.

% motion fails on nested parens/brackets of the same type.

Functionally no change, just much better style.

Closes #560

Fixed bug with duplicating formatted text in CSS/XML/JavaScript when only a part of the code, not the entire code, is formatted.

Closes #544

Slow, and problematic on several browsers.