support for multiple server url

[peteasa]

It seems that devicehive server supports multiple servers (frontend, auth ..) and so multiple url must be used to communicate depending on the relative url being used (/token/refresh, /device/, /devicetype, /network, /user, /plugin) . I propose that this support is added to enable devicehive-python-webconfig and user applications to be updated to make use of the multiple server ports.

I have proposed a possible solution to this https://github.com/devicehive/devicehive-python/pull/51/commits/909d2e4b7d1b7ec327e4a8ab15f7b31cef82a7ad.