[#1814] Mark - Remove redundant feature file

There are no longer suggested fields when adding fields to a form
section; all tests in the feature file had been @wip’d so there’s no
point in the file being kept.
[#1814] Mark - Move code into form_section_edit_page
[#1814] Mark - Move step to more logical place

The step was for a different page to the steps file it had been placed
in. Also updated to use the form_section_edit_page. Ideally it would
use a better selector and take the text on the page as an argument,
but this is a simple way of moving the step without adding that
complexity (and the step is only used in one place anyway).
[#1814] Mark - Move step to more logical place

The step was for a different page to the steps file it had been placed
in.
[#1814] Mark - Remove unnecessary step

The step wasn’t doing anything more than a step in web_steps.
[#1814] Mark - Move code into highlight_fields_page
[#1814] Mark - Move code into new_child_page