Bug 1017314: Load tutorial config in a preload method.

* .. plus new unit tests and a missing(?) setup.js to load MocksHelper and loadBodyHTML,
* start tutorial preload in ftu UIManager.init

Expecting some (ostensibly unrelated) FTU unit tests might fail, I'm confused about how they are passing at all without the setup.js this PR adds? 

Some of the tutorial.js changes were necessitated by the addition of the Tutorial.reset() method, which in turn is really only required by the need to test the preload() method. The patch could be simplified if that's not necessary here. Though I think it might be a good thing in the long run, as it would be great to be able to allow users to re-run the tutorial at any time