[Yt-dev] parameter file store

[Matthew Turk]

Hi guys,

I rewrote -- again -- the parameter file store.  This one I finished a
couple weeks ago, and Dave, Britton and I have been testing it since
then.  (Implicitly, no less.)  I'm committing it now, and it comes
with new unit tests for the parameter file store.  I think it's more
robust than the previous one, and it works in parallel.
Unfortunately, it might grind the disk slightly more, but I think it's
on the scale of MUCH less than reading/writing the normal .yt file or
parsing the hierarchy.

Let me know if you have any problems; I committed in r1196.

I updated the unit tests, but unfortunately I can't quite figure out
how to run them without having instantiated the parameter file once
yet.  Specifically, Clearly this means I'm not an expert at writing
unit tests or mock objects.  Anyway, you can run them by first
instantiating an EnzoStaticOutput of tests/DD0010/moving7_0010 and
then doing tests/test_lagos.py.  Sometime I'll see about writing some
more of those, too.

If there are any edge cases or problems, let me know.  I wrote up (by
copying a couple paragraphs from my thesis and extending them) a bit
of why we need this, how it works, and what it does.  This is the kind
of tone I was thinking of; do y'all think it works, or should it be
scrapped?  http://blog.enzotools.org/  It will likely not get read --
that's pretty clear -- but I think it's a useful means of collecting
information that can be processed back into documentation.

-Matt