Resize/Migrate functions for PowerVM driver

Added resize and migrate functionality to PowerVM driver.
Allows resizing of instance and cold migration of
an instance to different host.

bp powervm-compute-resize-migration

Change-Id: I723456266d3ceb4bd4a7ce4273008201b450f533
API extension for accessing instance_actions

Adds a new API extension for accessing the recorded actions and events
on an instance.  Usage is documented with api samples.

Additionally it modified the db api to retrieve actions by request_id
since the api does not return the db id.  This extension is the first
consumer of that method so there's no issue of changing behaviour
elsewhere.

Blueprint instance-actions
DocImpact

Change-Id: I74109586cc762a7f51d2b114896cf071ee0671cb
Merge "Resize/Migrate functions for PowerVM driver"
Merge "API extension for accessing instance_actions"