Compatibility fixes to enable Platform to build with the latest Autowiring without modifications

- Adding operator bool to auto_in, marking it as deprecated and setting it to trivially return
- auto_in is now based on a shared pointer, without loss of generality
- AutoFilter instances should be able to accept undefined types as inputs
- Argument types are identified by the auto_id metatype rather than directly by their type
- It should be possible to inject an AutoFilter even if _none_ of its arguments are defined