Added a fix for issue Jenkins JENKINS-22325. The issue is that when using the 'build' URL to trigger a job without parameters we don't jsut a JSOn response back. This makes sendHTTPCall fail when it tries to create a JSON object out of the response. The fix is to check if the response is empty and if so return null from sendHTTPCall. This means any call to sendHTTPCall will have to be checked for 'null responses.
Removed URLs from console output (as per previous security concerns comment) and added some in-code commments to help other developers
Merge pull request #3 from timbrown5/master

Fix for JENKINS-22325