Update neptune docs on how to use appman package tags with deployment server for apps with c++ plugin

Use of tags should be documented as a general approach of querying apps from deployment  server for platform dependent apps (e.g. with c++ plugin):

1. Add sample of adding extra tags to package
2. Add description of agreed tags format for neptune
3. Add description or reference to deployment server docs for query with tags
4. Add reference to Alexa app or extra apps as an example of app with C++ plugin