Disable view rendering by default in functional tests

Code here mostly based on how rspec does it (where based on means copied from).  We allow for labelling a specific test as a view test and for that to actually render views.  Now to go and label all the tests...
Fix macro-style functional tests to use view_test where needed
Mark all functional tests that need a rendered view as a view_test

Mostly this is any test that uses assert_select or css_select or similar.
Merge pull request #186 from alphagov/view_rendering

Don't render views in functional tests