Bug 1983 fixed: added the possibility to deploy bundles from the Charm Hub

Also upgraded the version of the juju library to 2.9.8 (and made the
necessary changes to the code to work with this version), once the
previous version didn't supported Bundles from the Charm Hub

Change-Id: I34d87dff75b4e77fdbdaef0eaf4da565b0bf213b
Signed-off-by: Pedro Escaleira <escaleira@av.it.pt>