add option to custom colur ng-directives

[kkozmic]

Not sure how complicated it would be but, it would be nice to have color identifiers-like option to have custom color for the angular directives (ng-something) in my HTML to make them stand out

[citizenmatt]

Would you want the attributes highlighted, or the attribute values? I've just completed a change that gives us an AST for the attribute value. This gives the ability to provide some highlighting (e.g. keywords and if "colour identifiers" is enabled, properties). What would you want?