Update routing for check creation

[ckbedwell]

Note this should be addressed after the check creation redesign has been merged.

Problem

Currently our routing for check creation is confusing and unpredictable. The breadcrumbs in-app don't represent the URL routing and it is impossible to go back to the 'Add new check' page.

Completion criteria

Update the check routing so it is predictable and each step of the process is easy to navigate by both breadcrumbs and modifying the URL directly.