Add type safety to registration/resolving.
When registering elements identified by name, we might leave literal strings in the code and/or keep a list of string identifying registered element. But there is not safety in case of changing an element type at registration without updating resolving, or any other way of switching types/string.

This PR adds:

• TypeIdentifier protocol to associate a type to a string name
• Identifiable protocol to statically bind a registrable type to aTypeIdentifier
• DedicatedIdentifier to bind types which can not extend a protocol such as protocols
• entensions over Container and Resolver to use this type safe identification on top of literal string naming