add default action configs per cluster

Similar to hadoop configs per cluster, Oozie should support default action configurations per cluster.

This default config per action per cluster mechanism would act as defaults for the action configuration section enabling things like:

• defining a special queue for launcher jobs
• setting properties required to tune pig/hive etc

It should load/work in identical way as the hadoop configurations but instead using just a 'host:name' key it would use a composed key 'host:name + action-type'