Improvements to navigation

People are still failing to complete the safety stages of registration.

This change adds styling to the 'tasks to be done' sections of the main navigation template to try to make it even clearer that there's more than one thing to be done. Because this trains the user to take action on items coloured pink and therefore they may now ignore everything else, I've also styled the reminder about getting a photograph taken to match even though it's something that happens outside this system.

The submit button text on the personal details form is also updated to imply there are subsequent tasks after that form is submitted.