Reduce docstring line lengths for webapi unit tests.

An annoying thing about submitting webapi unit test code for review is
that ReviewBot would be very sad about the docstring line lengths. These
were long because unit tests, by default, only show the first line.
However, that's under our control, it turns out.

Now, the new base TestCase will grab the summary, even if it's wrapped
across lines, and turn it into one line.

All the docstrings have been updated in the webapi tests for this. The
rules I used for formatting them is as follows:

1) If it can fit on one line, then keep it on one line.
2) If it needs to wrap, wrap the details part after "API" (such as
   "with ...") on the next line.
3) If it still needs to wrap, wrap the "METHOD URL API" part onto its
   own line, keeping it together as much as possible.
4) If it still needs to wrap, break that part up as needed.

Some URLs are long enough by themselves where they will still trigger
warnings, but this is limited to only a few instances now.