add support for main css override defined in front YAML

just add css variable in front YAML with the name of the main css file to load
add DAMapping page with several documentation subpages (for a start)

add DAMapping index pages
create damapping specific page template
create damapping specific css file
add damapping logo and specific feature image
justify text of DAMapping pages by default
add images to home page of DAMapping
little change of colour in damapping feature image
add TODO for missing excerpt
done TODO find way to add twitter links under author picture

add links on all tips and articles
add links to draft file template + comments disabled