Modified routing logic and controllers, to support static (About, etc) pages

NOTE that this includes a new routing file (SITE.routes.py) that must be placed in the *site* root of web2py. It uses the newer "parametric" router to gracefully remap slashes (hyphens) in URLs to underscores in web2py controller+action names.
Adding site-wide routing tweaks to README file
Tweaks to README
Removing unused files for the old plugin_wiki.
Revised routers and README file. Linked navbar to static pages.
Added missing controllers and views, cleanup of headings site-wide.
Rough layout for Credits page.
More rough layouts for static pages (incl. side menu for About pages)
Improved styling of left-hand nav in About pages.