FPCF Tutorial for Website

[errt]

Adds a tutorial for the fixed-point computation framework to the website.
Includes changes to the site generation and templates to allow for pages outside of the top level directory.

[svenkeidel]

@errt, how can I build the tutorial documentation?

[errt]

sbt generateSite, then look for it in target/scala-2.12/resource_managed. However, viewing this locally won't work very well.

[svenkeidel]

Thanks for the hard work you put into this tutorial.

The main point you can improve: It is hard/impossible to understand some methods, because their code is scattered across multiple pages. Readers have to stitch these listings together in their heads. I propose you show larger coherent listings and refer to specific code pieces by line numbers.

Here is my detailed feedback: opal-tutorial.pdf