Move test Solr instructions into a script

These will just rot horribly if they're not actually executed on a
regular basis…
tests: update requirements to match tox
Tests: update Solr schema to match current build_solr_schema

* Added fields used in spatial tests: location, username, comment
* Updated schema for recent Solr
* Ran `xmllint --c14n "$*" | xmllint --format --encode "utf-8" -`
Tests: update test_quotes_regression exception test

This was previously relying on the assumption that a query would not
match, which is Solr version dependent, rather than simply
confirming that no exception is raised
Tests: update test_more_like_this for Solr 4.6
Docs: fix ReST syntax error in searchqueryset_api.rst
Fix bounding box calculation for spatial queries (closes #718)

Thanks @jasisz for the fix
Whoosh: allow multiple order_by() fields

The Whoosh backend previously prevented the use of more than one
order_by field. It now allows multiple fields as long as every field
uses the same sort direction.

Thanks to @qris, @overflow for the patch

Closes #627
Closes #919
Allow users to pass in additional kwargs to Solr and Elasticsearch backends

Fixes #674, #862
Doc formatting fix