Allow customization script to be uploaded

[Adrien Cunin]

When creating a new instance, it would be nice to be able to upload a customization script, rather than filling out the text area.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/118316

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/118316
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=c2594b3d0ead60a7afe79f374056c3a0c66de12d
Submitter: Jenkins
Branch: master

commit c2594b3d0ead60a7afe79f374056c3a0c66de12d
Author: johndavidge <email address hidden>
Date: Tue Sep 2 03:52:43 2014 -0700

    Instance customization script can now be uploaded as file

    Added the ability for a user to upload a customization script file from
    their local machine instead of copy/pasting it into a text field if they
    prefer.

    Tests are included to cover this new functionality.

    Change-Id: Icc0e750346822a26ea853d4cc3d790d9d9f289d5
    Closes-Bug: 1298483