Update review page

- [x] Remove subsections
- [x] Remove stale i18n translations (Waiting for @Demwunz to finish some i18n work)
- [x] Fix dates to use GDS standard format, e.g. 15/01/1985 -> 15th Jan 1985 
- [x] Check with all fields are represented on the review page
- [x] Conditional disclosure of elements, e.g. don't show rows pertinent to pay if claimant wasn't employed
- [x] Styling (@demwunz)
- [x] Remove dead CSS, e.g. subsection headers (@demwunz)