Bug 1049916 - Create Firefox Accounts smoke tests to validate user authe...

...ntication R=spenrose
It seems like the tests are largely duplicated across test files, and the variation is just how you open the fxa system dialog.

This will quickly lead to bugs where one test gets a bug fix, but we forget to apply the fix to other functions.

I think it would be reasonable to verify that each of the starting points takes you to the FxA dialog (say, by verifying that the fxa iframe is topmost/displayed). Then we can just have one test that runs through the various FxA flows without duplication.