Added a "header" YAML front matter.

This is in preparation for refactoring main.html to be a generic
default html page.
Moved menu items from main.html layout to index.html

Continuing with the main.html refactoring.
Eventually main.html will be default.html and that layout will be
used for the entire site (all two pages).
Replaced header front matter with title
reformatted post layout to my liking
renamed the project
Renamed main.html to default.html