Change Attributes to use kebab case?

[istathar]

In many usages, role names can have - characters in them. Indeed, some even prohibit _. We have no need to change this, per se, but it is tempting to have a slightly different character set from Identifiers, which admit snake case _, to one which admits '-', also known as kebab case. That would provide some visual distinction for Attributes as compared to Identifiers, though certainly single words in lower-case would be ambiguous (that's not a problem for parsers because of the leading character).