Story format CSS split + engine improvements

* Sugarcane and Jonah: separated all of the engine-specific CSS from the
stylistic CSS. The intention here is that the latter can in future
versions be foregone entirely and replaced with something else if the
author chooses.
* Changed all the element onclick references to
addEventListener/attachEvent calls.
* visitedTag() can now take a string of space-delimited tags, as an
alternative to several strings or an array.
* Added random() from Twine 2 and SugarCube.
* Fixed a bug where Jonah would crash when restarting a story.
* Added a "javascript:;" href to Jonah toolbar links which normally do
not have one.
* Added an Object.create() polyfill, primarily to make clone() work more
consistently.