Dates in URLs and document meta data

Updating the dates to follow the [discussed format](https://groups.google.com/forum/#!topic/growsdk/GBVe6CTTfrE) and to act like titles in the document front-matter.

At the same time the serving path logic has been updated to detect usage of the `dates.date_name` format and format the date accordingly.

Also removing the `published` since it is old school.