Allow non canonical values for Enums - #106

RFC7643 §2.3.1 only allows service providers to restrict string attributes
to their canonicalValues, so attributes suggesting canonical values now keep
arbitrary values instead of rejecting them. This covers the type attribute
of Email, PhoneNumber, Im, Photo, Address and AuthenticationScheme.

Canonical values are matched case-insensitively, as §2.2 makes those
attributes case-insensitive, and their JSON schema advertises the canonical
values as examples instead of a restrictive enum.