Add Page Object Models
Handle advisor pre-qualification

All 3 questions must be answered "yes"
Spec gardening

* Replaces double quoted strings for consistency
* Use `is_expected` instead of the outdated `should`
* Change the `subject` and use `be_valid`
Changes terminology to match the story role
Introduces `Principal` scoped resource

This now matches the latest version of the 'Principal answers
pre-qualification questions' story.
Merge pull request #5 from moneyadviceservice/advisor-pre-qualification

Principal pre-qualification