DRILL-8204: Allow Provided Schema for HTTP Plugin in JSON Mode (#2526)
* Initial commit
* Map working
* WIP
* Added builder
* Lists in maps working
* Add documentation
* Cleaned up UT
* Final Revision
* Fix checkstyle
* Minor tweak
* removed extra test file
* Removed unused import
* Added inline schema support
* Addressed review comments
* Removed unused import
* Removed json string
* Final Revisions
* Fixed unit test
