Initial code import with most plugins for a useful site

Signed-off-by: Maxime Petazzoni <maxime.petazzoni@bulix.org>
Fix reading time computation

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>
Documentation

Start writing the Pandagen documentation, including plugin
documentation. Just need to go down all the implemented plugins and
finish documenting them now.

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>
Flake8 fixes

Signed-off-by: Maxime Petazzoni <max@signalfuse.com>
Updates to the Watch plugin, but still disabled for now

Signed-off-by: Maxime Petazzoni <maxime.petazzoni@bulix.org>
Extract the list parsing as it might be useful for other plugins

Signed-off-by: Maxime Petazzoni <maxime.petazzoni@bulix.org>
Markdown parsing improvements

* Add a CSS class to all content images
* Add Markdown Smartypants for automatic typographic fixups

Signed-off-by: Maxime Petazzoni <maxime.petazzoni@bulix.org>
Add Serve plugin for development serving

This plugin is meant to be used at the end of the pipeline and starts up
a small HTTP server serving the build output directory. To stop serving,
hit ^C.

Signed-off-by: Maxime Petazzoni <maxime.petazzoni@bulix.org>