CSV generation code should be reusable

[Rob Raymond]

Currently usage has defined some helpful classes to generate downloadable CSV data. This code is general purpose but it lives in openstack_dashboard/usage module.
In order to use it in other dashboards, it should be moved into utils module.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/73731

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/73731
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=9ad412827b0e9c1eeeab602e24181e20c61816a3
Submitter: Jenkins
Branch: master

commit 9ad412827b0e9c1eeeab602e24181e20c61816a3
Author: Rob Raymond <email address hidden>
Date: Fri Feb 14 15:36:14 2014 -0700

    Refactor CSV generation code to utils

    Moving general CSV generation code from usage into utils so that it can be
    used by other dashboards.

    The file is named csvbase to avoid name collisions with csv module.

    Change-Id: I3f4a573b53cb2d85fa36e84320707d74917498ad
    Closes-bug: #1280475