Rewriting functions using sass 3.3 maps in order to handle deprecation warnings more intelligently

I've been trying to get rid of colour deprecation warnings from forms. I found that even after updating use cases some deprecation warnings were still showing because e.g. in `oColorsGetColorFor(form-label-error error, border)` - the old use case for `form-label-error border` is deprecated but `error border` is not deprecated; sass threw a warning as soon as it encountered something deprecated. And, even more problematic come to think of it, it probably used the deprecated use case instead of the non-deprecated one.

So I ended up getting sucked in and doing a major rewrite using sass 3.3 maps. Please review and merge if happy. The code can probably be simplified, and one thing in particular to look at is lines 15-16: I think the 'all' functionality was mis-implemented before (see 30-31 vs 13-14 of the old file), but I'm not 100% sure if the way I've rewritten it matches the documented behaviour. @dansearle-ft @triblondon