Add publications to the website.

The publications page is fed by python/firedrake_docs/source/_static/bibliography.bib. Adding references to that file and republishing the website will update the bibliography.
New logo in icon.ico
Working towards having a documentation page and a demo!
Modifications to build, layout etc for the documentation docs.
Complete helmholtz demo.
Import pylit wholesale.
The Helmholtz equation, complete with automatically generated executable version, now appears on the website.
Shut up pylit about other people's code.
Add struck-out surface integral term in Helmholtz demo

The magic incantation is to \require{cancel} and then \cancel{foo}.
Move conflicting filenames to appears case-insensitive filesystems