OpenNebula

Attached is a patch which allows for system administrator provided dynamic costing to the showback code.

It calls out to an executable (here named "aurae-calculate-showback-extra") to compute the cost per hour of the given history record, it provides the VM ID, CPU, memory, and the history record as a base64 encoded string.

This can be used, in conjunction with forcing the CPU and memory cost, to provide a completely flexible costing model for the showback system.

This implementation is not the same as most other OpenNebula drivers, where a socket is created with a daemon on the other side and commands are sent over that socket, instead the process is executed directly from OpenNebula which may not be ideal.