Link CSS simplification + header alteration

* Altered the header link CSS to simply use ".passage a", which covers
internal links, external links, back, return, and HTML external links.
The example stylesheet CSS has been altered to use this same
formulation, too.
* Targets can now put the string "STORY" (in quotes) in their HTML code
to have the story's storeArea divs inserted there at compile time
instead of being merely appended. All built-in headers now use this.