Handle case where item may not yet be created.

Just a slightly more robust construction, more for development than
end-use patterns.
Add a few more parameters to Download output.

I could implement these more quickly, but I'm adament that the output be
well-formatted.  In particular, if a human needs to debug something,
I believe that columnar alignment is important.  Luckily, the design
pattern is now in place, modulo generalization.
Update to Django 1.6 API

transaction.commit_on_success is deprecated in favor of
transaction.atomic.  In this case, deprecated also means "not working"
for at least SQLite, so update ahead of schedule.
Another 4 parameters completed in Download Dat
Four more paramters implemented in download.

Six more to go.  Unfortunately, I apparently forgot all about
CapacityFactor, so I have to implement that client side first.
Need to profile first.

Distinct ought to be used after it is shown to be necessary, not before.
Apparent typo in TechInputSplit Form.
Two more parameters in download_as_dat.  Four more to go...
Two more download_as_dat parameters complete.
Two more parameters.

Okay, just two more to go: CapacityFactorTech and CapacityFactorProcess.