Fixed bugs, 'fix_open_tags' now uses pytidylib.

Several bugs introduced with the newer features.
Some surfaced in old features after using them
in a different way.

Ads were changed to be template based.
Css was cleaned up for the ads.

htmltools.fix_open_tags was broken when parsing
new output from the 'highlight' template tag.

fix_open_tags now uses PyTidyLib.

Small bugs were fixed in main.html (featured blog link).

Project pages now use the 'ad_{ad-type}' template tags.