Introduce a testrunner that dynamically makes a DXR instance, for simple, single-file test fixtures.

* Pass -s to nosetests by default so we can see output and pdb breakpoints.
* Rename old test files so they're more uniquely named and thus findable in LaunchBar.
Port callers and called-by tests to the new harness. This lets us delete hello.h.

Also switch assert_query_includes to check the full set of returned results. I think the inclusion thing was a bowing to overly tight fixture coupling. Rename it for consistency with found_line_eq.
Port member tests to the new harness, etc.

Rename json-test/HelloWorld to "code" so all the tree names in the tests are the same and we can just hard-code "code" in the search URL search_results() uses.

This lets us remove the "*member*" and "BitField.h" files from json-test. Now we're getting somewhere.
Make test harness good. https://wiki.mozilla.org/Better_DXR_Testing

Now it's easy to make a new test: no FS boilerplate. As a result, there's much less temptation to couple them together.

You can still have the testrunner spit out a DXR instance to the FS so you can serve it up and play with it (should_delete_instance = False).

Ported a bunch of the json-test tangled ball to the new harness. There's still more to come, but we might as well merge what we have so folks can write good tests for new features.