Added error_description field to error responses
Replaced res.json with res.send
Should return user display name in access token description
Merge branch 'develop' into add-error-info
Use jsonschema to validate input JSON data
Added error_description to unsupported_grant_type error response
Simplified code
Added middleware function for JSON schema verification
Use res.sendErrorResponse for unsupported_grant_type
Merge pull request #49 from ebu/add-error-info

Added error_description field to error responses