Fixed requesting a nonexistent doc throwing an exception.
Added simple stress test page /test/test.html
Fixed race condition with two similar search requests.
Fixed bug in simple stresstest app.
Made /docs without a filter return all documents.
Removed extra root element from doc-pid/contents response.

Now the contents response is equal to the original XML, and not
surrounded with "blacklab-response" tags.
Added stub for new indexName/fields/fieldName resource.

(To be implemented)