Added a test for a bad patch request
test that referer errors get json bodies

Shouldn't need to check it for other http errors
Use json response for http level errors

rest errors (inside jersey) will use json already.
merge ScottDugas: Rest respond json on error

Merge pull request #1556 from ScottDugas/sql-layer/rest-respond-json
https://github.com/FoundationDB/sql-layer/pull/1556