JCLOUDS-699: Properly deprecate OpenStack Nova zonescoped package

This PR deprecates the `org.jclouds.openstack.nova.v2_0.domain.zonescoped` package in favor of the `org.jclouds.openstack.nova.v2_0.domain.regionscoped` package and provides some other minor cleanup.

JIRA: https://issues.apache.org/jira/browse/JCLOUDS-699
See comment above