Add functions for uploading, listing, and removing OVA images to the API
and CLI interfaces. Includes improved parsing of the OVF and creation of
a system_template and profile for each OVA.
Also modifies some behaviour around profiles, making most components
option at creation to support both profile types (and incomplete
profiles generally).
Implementation part 2/3 - remaining: OVA VM creation
References #71
Allow the user to specify other, non-raw files and upload them,
performing a conversion with qemu-img convert and a temporary block
device as a shim (since qemu-img can't use FIFOs).
Also ensures that the target volume exists before proceeding.
Addresses #68
Implements a "maintenance mode" for PVC clusters. For now, the only
thing this mode does is disable node fencing while the state is true.
This allows the administrator to tell PVC that network connectivity,
etc. might be interrupted and to avoid fencing nodes.
Closes#70