Add the auth_encryption_key parameter to the heat::engine call

More recent versions of the puppet-heat module, starting in Dec '13,
require a auth_encryption_key parameter to be passed to the engine
class. Kickstack didn't pass on the parameter, which caused the
installation of Heat to fail. This commit adds the parameter, sets
it automatically and exports it as fact.

Applying this fix makes deploying Heat via Kickstack possible again.
Add database configuration to neutron.conf

Previous versions of Kickstack would have the database configuration in
the plugin. By now, apparently, the recommended mechanism is to have the
DB configuration happen in neutron.conf -- at least the ML2 class of the
Neutron module doesn't even implement database parameters anymore. Thus,
we need the database configuration in neutron.conf. This commit adds the
required parameters to the neutron class.
Bump dependency on puppetlabs-openstack to 4.0.0