Change JsonUtils to throw two new exceptions JsonReadException and JsonWriteException. Also, in REST module, maps Json read errors to HTTP 400 (since client sent bad data) and Json write to HTTP 500 (since server is at fault).

USERGRID-2339 "JsonUtils.java should not silently fail"
https://apigeesc.atlassian.net/browse/USERGRID-2339
Formatting and import org.
Don't HTTP status 2xx and 4xx as errors, only 500 and above.
https://apigeesc.atlassian.net/browse/USERGRID-2361
Merge branch 'master' into USERGRID-2180
Merge pull request #231 from apigee/USERGRID-2180

Usergrid 2180 - Error handling improvements