refactor: introduce idl-v2

[techraed]

idl-gen TODOs:

• implement generation (template/snapshot) tests
• discuss generation logic for reference/boxes, paren types, generic consts -> UPD: TypeInfo erases references, generic const remain the way we generate it, paren types are unwrapped.
• discuss skipping docs for tuple struct field, if it's the only field
• discuss extends section and new semantics for it (calling base service method using standard routing <- taking max of routing, allows stating in IDL which method is overriden (solidity has loud override semantics)

UPD: The code is injected with TODO [future] stuff which references a new sails binary protocol, which will change the logic in those places, where that "todo" is stated.