Dasherize all Sass mixins

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Living Style Guide: Fix variable name

[ci skip]

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Revert "Living Style Guide: Document OpenProject colors"

This reverts commit 91b6bc130dc462595b22c909f6ce41a265418797.
Remove unused OpenProject colour variables

This partially reverts 2504a873f6cd7405314b595c6ead1b4c96568baa

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Rationalise Colour variables

Signed-off-by: Alex Coles <alex@alexbcoles.com>