Import Font Awesome for icons

Update roadmap
Implement fixed surname, forenames sorting of candidates in an assessment
Add validation to the assessment domain model
Split assessment editor from assessments controller
Improve assessment editor validation feedback
Improve grade boundary validation
Refactor assessment editor models and validation

Move editor models into separate namespace.
Move validation methods into the view models.
Improve styling consistency

Make more use of Font Awesome icons.
Housekeeping: remove unused files and clean code
Implement basic excel export of an assessment
Add exported excel workbook styling
Implement assessment excel export from web editor view
Update roadmap, disable search box and button
Refactor user repo into isolated stack

Extract interfaces for user repo and user aggregate.
Remove unused repositories
Move common service components to root of the project
Refactor grade boundaries repo into isolated stack

Extract interfaces for grade boundaries repo and user domain models.
Remove more unused service classes
Refactor assessments repo into isolated stack

Extract interfaces for assessments repo and assessment domain models.
Allow web controllers to have repositories constructor injected