Update app stylesheet, remove hardcoded favicon

New version of stylesheets now with pygments styles.  Favicon now uses
FAVICON configuration parameter to set path.
Move utility templates to prefix '_', add footer utility templates.

Utility templates moved to have '_' prefix similar to how sass files are.
Aditional templates for article and page footer contents now used to load
comments etc.
Update all main template files

This is a major update to template files as now most have actual content.