Notification of promotions

This change notifies the user when a build was triggered by promoting another build. The box will change color and display a short text message as shown below in the picture. 

In order to get this effect you need to pass two variables during the promotion process, BUILDGRAPH_PARENT_NAME and BUILDGRAPH_PARENT_NUMBER, which, as seen below, are equivalent to the promoted builds variables $promoted_number and $promoted_job_name. 

![bg_example](https://cloud.githubusercontent.com/assets/8010352/3892296/43774b5c-2231-11e4-88fb-0e428cf5f358.png)

![bg_example_two](https://cloud.githubusercontent.com/assets/8010352/3892396/f9deaf20-2231-11e4-9b3a-73c86ac47450.png)


[Reference: In the flow chart above, test-1 automatically calls test-2, but also re-calls test-2 when test-1 is promoted. Same process for test-2 -> test-3. This was done to show the difference between a regular trigger and a promoted trigger.]