BP mistral-actions-design (ad-hoc actions in factory)

* Fixing action factory to create ad-hoc actions if needed
* More tests for action factory

TODO:
* Refactoring executor to use new action infrastructure
* Remove old action infrastructure
* Action plugin architecture

Partially implements: blueprint mistral-actions-design

Change-Id: I69946989226a1c05ed089acccb7e10a6516cf966
BP mistral-actions-design (switch to new design)

* Refactored action_factory.py (adhoc actions into a separate method)
* Fixed task db model (service_spec -> action_spec)
* Fixed workbook model (tasks, actions, Service -> Namespace)
* Fixed all tests related to DSL syntax changes

TODO:
* Fix all samples in mistral-extra
* Action plugin architecture

Change-Id: Iac6317dde894f17c81332a8c9a2397b70448f6b2