Basic page and plugin relationship integration.

- Saffron now organizes content output by pages, and the content therein
is modularized as "plugins."  A page can have an arbitrary number of
plugins on it, and the plugins define the HTML output that a page
provides.  This allows you to organize and sort content per-page in a
modular fashion.
- saffron.inc.php now integrated to include all of the saffron-core
libraries in the correct order.
- Current version of index.php showcases basic plugin functionality and
can be used as a master reference to show (roughly) how the final
product will output HTML to the browser.