Full charm support

This work adds the ability to deploy charms directly to an
externally instantiated VM, which is expected to have N2VC's public key
injected into it, by using the VCA's manual provisioning function.

This allows the VCA to ssh to the target machine and provision it. The
charm will then be deployed directly to that machine, allowing the charm
to fully manage the VNF lifecycle.

Change-Id: I935e432fbd60a9a6bc10a499ae1b8e07c1e70c14
Signed-off-by: Adam Israel <adam.israel@canonical.com>