Fix broken build.
Allow signature analysis to ignore current Node.

This allows us to test code-completion potential by pretending the current node hasn't been written yet and allowing us to see if it would have been predicted by code-completion.
Refactored interface type recovery into separate packages.
Encapsulated CallTargetSignatureBuilder as package class.

InterfaceRecovery is the new public interface.
Basic test of code-completion ability.
Compare code completion using type info from different sources.