[SPEC] Fix directory email verification token spec
[SPEC] Email verification token for the account should be nil by default if the registraion workflow isn't enabled
[SPEC] Added more and fixed Custom Data specs
Association should return nil if the association is null, unless it's custom data
Added ignore_camelcasing option in the base class, so Custom Data can work normally
Ignore camelcasing when saving custom data resources
Changed execute request method parameters