SCSSLint: Fix DuplicateProperty

Probably left over from a merge resolution
SCSSLint: Fix DeclarationOrder

Keep rule selectors together
SCSSLint: Fix HexFormat

Use lowercase and shortest possible hex colours
SCSSLint: Fix BorderZero

Use zero rather than “none” for clearing border
SCSSLint: Apply ColorKeyword

Use hex codes for colours, rather than named colours
SCSSLint: Enable CapitalizationInSelector

Need to exlude the social media centre because of overriding the
dataTables class
SCSSLint: Apply PropertySortOrder

- Alphabetizes properties
- Removed very old FF vendor prefixing from messages.scss since the
support for those was long since dropped