provide restful api and CLI for valence project

As we known, valence project is a collection of all things Rack Scale Control,
which can consider computer, storage and network as disaggregated resource
that can be composed on the fly to meet various needs in a data center or
cloud.

But there have no valence client for user to call the valence api gracefully
or get information conveniently in console as other OpenStack "Big Tent"
project. So not only it's necessary to provide a valence client for user but
also for valence developer.