228-rest client

This PR add a first version of the rest-client functionality of Poulpy.
We finally got restish to work, so we'll use this instead of our poor custom made solution openapi2cli (which can still be used if we need a black box CLI for Ing1).

Some important considerations:

• restish can be configured with a JSON file, so for this 1st version we'll use the same format for Poulpy config file and refresh restish config with it before each call.

• We can use an URL to specify openapi files, those files are automatically re-sync every 24 hours by restish. They can be updated with restish api sync <SRVC>.