Test to compare the performance of MMV and the Commons File: page

- Runs combinations of cold/warm browser cache and average/large window size
- Sends events with EventLogging that will allow us to generate limn graphs

This should run separately from the other cucumber test we already
have. This one needs different environment variables  because it needs
to run against production wikis instead of beta wikipedia

Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/378
Change-Id: I53b521ca2759c493aae6fe6e59be8d448e0f15d7
Merge "Test to compare the performance of MMV and the Commons File: page"