api: improving overview document to describe what classes & methods are
minor
- api: removing unnecessary 'Definition' header
- api: adding RClass class definition
- api: merging RClass class methods onto the RClass page
- api: renaming the RVariable file to be more sensical
minor edit
api: updating classes & methods overview and correcting reference toctrees
edits to resolve build errors
css: tweaking to use more of datavyu site's styling
api: making landing pages less boring
api: editing landing page and adding more images