User management UI

- Add validation
- Add basic user API
- Select multiple programmes and projects.
- Load selected user's data.
- Static page when saved.
Fixes after code review.
Merge pull request #163 from MastodonC/feature/user-mgmt

User management
Add documentation

- Document measurements validation.
- Document conversion factors.
- Document datasets API
Merge pull request #166 from MastodonC/feature/docs

Feature/docs
Update documentation link.
Merge pull request #167 from MastodonC/feature/doc-link

Update documentation link.
Parse multiple entities and profiles from a csv.

One csv should be able to create a whole project full of properties.