Add response status and content to DiamondashApiErrors.
Fix diamondash client tests.
Proxy diamondash errors to the client and test.
Construct DiamondashApiError message from status code and content.
Merge branch 'feature/issue-856-pass-diamondash-errors-on-to-diamondash-client' into develop
Fix CSS styling for nav bar item right-hand borders (@justinvdm).