Fluid Mechanics: Navier-Stokes: 1D-0D example

Hi Andre,

This compiled locally for me in sphinx without issue. But a couple of notes:

* I just realized this branch also includes some other undocumented Navier-Stokes example commits that aren't really relevant but shouldn't affect anything for the purpose of this branch. If it matters, I can resubmit a new pull request with just the 1D-0D example in a separate branch.

* I wasn't really sure about how we want the example doc naming convention but I just went with the examples folder tree as seen in the pull request title. However, I suppose we'd actually want to have some reST for each example tree level so it looks like a nicely indented outline in the doc TOC?

* I put in a literalinclude snippet that includes the whole CellML model mapping for my example. Depending on how this renders in readthedocs we might want to cut this down significantly.

Let me know if there are any other issues/questions.

Cheers,
David