Fix capitalization of VMBuilder and improve wording

The proper capitalization is VMBuilder, let's use that.
Reference: https://launchpad.net/vmbuilder

I've updated this with suggestions by Diane Fleming (thanks!)
to improve the overall section (now really part of this set).

Change-Id: I9912c6e544c49f10f1214eee9c4735d79a2a34f6