cyclades: Introduce project field in Volume

A volume is a separate resource and is assigned to a project.
cyclades: Add serial field on Volume

Add a field on Volume to store quotaholder serial in order to handle
commissions.
cyclades: Remove unused quota code
cyclades: Compute disk quota per user/project
cyclades: Fix typos
cyclades: Specify project on volume creation

Allow specifying project when creating a new volume. On a VM creation, the
system volume is given the same project as the VM.
cyclades: First issue commission, then update project

When reassigning a resource, update the project field at the end. This keeps
the issue commission code more stable, because it can access the original
project.
cyclades: Add missing MODIFY_VOLUME action

Handle the case when a volume is modified in the backend.
cyclades: Support commissions on multiple projects

An action on a resource can now trigger quota changes on multiple projects.
For example, when a VM is destroyed, its attached volumes (which may refer
to different projects) are destroyed too.

Astakosclient commission helper functions are changed to take provisions
on project/resource pairs.
cyclades: Support project reassignment for volumes

Volumes can be reassigned through the volume API except for the system
volumes. These are reassigned as part of the VM they are attached to.