unregisterType() should remove particular registration

[elf-pavlik]

https://github.com/solid/solid-client#registering-and-un-registering-types-in-the-type-registry

profile.typeRegistryForClass() returns an array of registrations, profile.unregisterType() should accept reference to one of those registrations and just remove that particular one.

Renaming it to removeTypeRegistration() may make it more clear, also each type registration could have simply delete() method.