Idea: replace host and port with URI

[gleichdick]

@v4hn proposed to replace both warehouse_host and warehouse_port parameters with one single generic one, e.g. warehouse_uri.
With the uri parameters, the plugins have more freedom in how and where they store stuff.
Of course, this requires the adaption of all plugins (currently mongodb, and two sqlite implementations).

[gleichdick]

Sorry, wrong place!