new flags: --client-only & --client-language

[aastein]

This PR adds two command line flags to Wag, --client-only and --client-language

--client-only When used wag does not generate server code

--client-language Can be go or js. When used wag will generate only the client of the specified language.

Both flags can be used together or separately. When using both flags like so --client-only --client-language js, no golang models are generated.

• [x] Run make build
• [x] Run make generate
• [x] Update the current version in the /VERSION file.