Fixes to report-a-problem confirmation and errors

The markup for the report-a-problem form was changed in https://github.com/alphagov/static/pull/441
but the confirmation and error javascript code wasn't. This means that
those elements are misaligned and this change fixes that problem.
Report-a-problem: update error message copy

The support page was renamed a while ago to the contact page.
Merge pull request #445 from alphagov/report-a-problem-fixes

Report-a-problem fixes