HUE-820 [oozie] Display any workflow as a graph

Import a workflow from the Oozie XML definition from the API if there is no
Hue Worflow model associated with it
If the import fail no graph is showned and a message is added in the logs
Refactor views and model
Reuse import workflow
Make sure to delete the imported workflow
Make definition tab higher
Improve variable outputs HDFs link with guess_link
Add a negative and positive test