Integrate updated broker for Jenkins (BB-3633)

I have updated Robert Elliot's Jenkins broker to use the Jenkins api. In doing so I have made it easier to use with secured servers and with builds that require parameters. My fork is available here:
https://bitbucket.org/KitB/jenkins-broker/

It expects the following fields in service:

• endpoint: the protocol, hostname and port of the Jenkins instance. e.g. https://build.myorg.com:8080
• project_name: The name of the job to be run on the Jenkins server
• token: The security token for the job to allow scripted builds
• module_name: As in the original broker, this allows for a specific directory within the repository to be watched for changes
• user_id: the username to login as, required only if the server is secured
• api_token: the token corresponding to the above user id, again required only for a secure server
• params: The parameters that will be passed to a build (a dict, I believe)