QA: Lots of browser test fixes.

* Fix browser tests not expanding new topic form
* Add "Page has re-rendered condition around"
* Move no resource loader errors and page has fully loaded into all
  "Given I am on a Flow page" pre-conditions
* Rename "I create a X in Y" to more understandable names
* Update header test to match behaviour
* Reorganise "Created a topic" pre-conditions
* Correct feature names
* Replace leading "And" with "Given" conditions

Change-Id: Iafe67ae619f61c7bc1e3c90dd931c73760a33d88