* Improves handling of exceptions in Index Lifecycle
This change improves a few different aspects:
* If an exception occurs executing the lifecycle of one index it is caught, logged and other indexes are still processed
* If the lifecycle policy specified in the settings does not exist an error is logged
* Fixes the exception when the delete action is run which occurs because Phase attempts to update the phase and action settings for the deleted index. A `LifecycleAction.indexSurvives()` method is introduced which defaults to `true` but can be overridden to indicate whether the index survives following completion of the action.
* Adds test
This change moves the Action classes and referenced data model classes to the new :x-pack-elasticsearch:plugin:core project in preparation for splitting the x-pack features into their own gradle modules.
Note that the TransportAction classes had to be promoted to their own class file (rather than being inner classes to their Action) so they can remain in the plugin project (and will late be move to the `index-lifecycle` project when its created.
Tal Levy
Colin Goodheart-Smithe