Add human readable parameter descriptions to the API parameters

[Metallion]

Problem

Currently Sinatra-browse generates API documentation showing the parameter names and their possible values etc. but it's still not always clear what the parameters do.

Solution

Sinatra-browse has a feature to describe parameters. We should use it and fill in descriptions for all parameters in OpenVNet. https://github.com/axsh/sinatra-browse#describing-parameters