PR for comment: Templating experimentation

This is where I am at with the experimentation around sample building. There is a new includecode plugin, the video snippets are extracted into a larger sample file, and there is a generator which turns that into a more normalised template. This is very alpha, but does build and render currently. 

Adding _code directory in video for example.
Added include code support that extracted from named sections
Added basic sample builder to _sample directory