Oauth2 console

@Scarygami can you take a look at this initial draft of a console based google oauth2 client. Dont merge yet, want to take a second look later. Basically took out some parts of the pub oauth2 magic so google apis could be called from the console.  Check out the [oauth_example_console.dart](https://github.com/financeCoding/dart-google-oauth2-library/blob/oauth2_console/example/oauth_example_console.dart)

At some point I'd like to update the generator also to support calling google apis from console, also have a branch currently working on this [implement_console_client](https://github.com/financeCoding/discovery_api_dart_client_generator/compare/implement_console_client)