Dynamic return types using generics

[elchukc]

Only changes type declaration file. Code functionality unchanged. All changes tested while using the library in a project.
Changes can be viewed commit-by-commit to see how the final types were built up to. This is on top of #44.

1. Geocoding queries can be strings or address component objects
2. Infer return type is array if input is array, or record if input is record
3. If we know the keys of a record, recognize key types as those keys specifically
4. optional _warnings property on response objects

[MiniCodeMonkey]

Thanks for contributing with these improvements!