LIBCLOUD-296 : stopped state for compute nodes

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Update CHANGES.
Add the Hong Kong (HKG) endpoint for Rackspace

Rackspace has opened a datacenter in Hong Kong with an endpoint name
of HKG. This change adds the endpoint to the endpoint mappings for
the compute and loadbalancer packages.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Update CHANGES.
docs: Update upgrade notes.
Add missing docstring for a new node state.
docs: Update upgrade nodes.

Add a section about new NodeState.STOPPED node state.
Update exception which gets thrown if user uses an old Rackspace provider
constant.
Bump version to 0.14.0-beta2.
docs: Fix title underline.