Create Type.Api

[ityonemo]

This is the general behaviour of something which can supply a types:

following functionality is expected:

• fetch_spec -> gets a typespec, as defined in a module
• fetch_type -> gets a type, as defined in a module
• ...? of?

Should be generalizable to several different concepts:

• An "override" which lets you define how a type works.
• A "cache system" which lets you store as PLTs or in ets tables.
• An inferencing system which actually looks at the machine code to find the types.