Add/remove nova files

Delete files that are not needed.

Add back in some nova files that are needed.

Also, resync the gantt/version.py from the nova tree, we
need the new version of this file.

Change-Id: I48ab670502417d588eb8ffd6044667ed5a9e1560
Get gantt to pass unit tests

Mostly a matter of having the appropriate modules imported from
the gantt tree rather than the nova tree.

Note that code can still import from the nova tree but this is only
for non-scheduler related files.  Ultimately we will remove all
nova references from the gantt code but that is a future project.

With these changes we can now have Jenkins gate on the unit tests.

Change-Id: I3bcc9742cc9ab4188f67c2aa66ad97eca2bc08bb