Configuring Uwazi and Extension to work with preserve

WIP!

In order to enable Preserve features within Uwazi:

• Within the settings collection's only document, the features property should contain an entry for preserve with a host pointing to Preserve's URL and a masterToken entry with the Preserve's token used to create individual user tokens

Example:

 "features" : {
                "preserve" : {
                        "host" : "http://some.preserve.url.com:4000",
                        "masterToken" : "aa834fa237173618764abbbcdf",
                }
        }

The masterToken is returned by the yarn blank-state command on the preserve folder*. This token is also stored in the authorization collection, as mentioned in the main README.

• note: the service attempts to communicate with mongo on the 27019 non-default port, so if commands fail, you may need to start the service with ./run start:local in order to expose the port outside docker when doing development or quick setups)