Added configuration option to use floating IPs

If enabled, the server will attempt to allocate and assign a
floating IP to each VM it creates.
Otherwise, the server will use the VMs fixed IP address instead
(used only if the server is running within OpenStack).
Changed example config file and schema file.
Updated VM creation flow to allocate and assign a floating IP after
volume attachment.
Updated VM deletion flow to de-allocate a floating IP after VM
deletion.
Updated VM creation check for fixed IP; now checks for either
private IP or public IP.
Changed flow when destroying VMs again

Updated openstack.destroyVM to include floating IP de-allocation.
Added verbose log messages throughout openstack module.
Abstracted VM destruction/promise rejection process.
Updated proxy.js to reflect openstack simplification.