Wordinserter

Fix handling of background colors

Fix table cell range handling.

Don't do the formatting "x" hack unless there is actually a format to apply. Improved the speed of table creation.
Disabled spell checking for code blocks. All nodes now support an "id" attribute, and if it is specified in a
heading tag a bookmark is added with the ID attribute as its name. Hyperlinks also now support a bookmark if their
URL's start with a "", so `<a href="name">` would link to `<h1 id="name">`.

Majorly refactored the whitespace handling code. It not actually works :)

Fix line spacing after CodeBlocks. Added support for border styles in images, and for multiple constants (use the
`CombinedConstants` class)

Added support for CSS files! WHERE IS YOUR GOD NOW? You can pass a `stylesheets` array to `parse()` with some css
definitions and it will do the right thing.

Added support for images with data URIs. Passing an image with a src set to "data:mimetype,base64;DATA..." will work
as expected, by extracting the image from the data URI and saving it, before inserting.