Make code lens work

[JanKoehnlein]

Code lens works fine apart from opening the references:

The server composes a set of arguments of type URI, Position and Location[] for the editor.action.showReferences command (in goReferencesCodelens#resolveCodeLens). These are sent to the client, as such converted to plain JSON objects. The client, when trying to execute the command, validates the args to be instance of URI, IPosition and Array, which fails as they are plain JSON objects.

One solution could be to register a separate command in the theia-go-extension that is called instead and does the conversion.

[JanKoehnlein]

Fixed with 3287c4f