Generate the Server and Client interfaces

[TheAngryByrd]

Is your feature request related to a problem? Please describe.

https://github.com/ionide/LanguageServerProtocol/pull/49 only handled the types but we should also generate the interface/abstract classes for server and client

Describe the solution you'd like Extend the code generation mechanism already in place

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context Add any other context or screenshots about the feature request here.