[#585] Replacing imported JSON writing sources

* Replacing the imported JSON writing utilities
(https://github.com/akvo/akvo-flow/tree/develop/GAE/src/org/waterforpeople/mapping/app/util/json)
[#585] Deleting json.jar library + imported JSON source files
[#585] Remove unused import and new line
Merge pull request #628 from akvo/issue/585

[#585] Cleaning up JSON* classes