Abstracts and return of static content

* Abstract field was added to projects. It's just a text field at the moment.
* Templates make use of a method which returns either that field or a shortened first paragraph of the project's description
* Vignettes on landing page were removed and replaced with static content in the templates
* landing-page specific styles were removed

CSS classes were chosen with "meh" in mind -- just aiming to get the content present.
In that case, just do it here.