EST-415: converting to use new FixtureScript API.

* New EstatioFixtureScripts service (inherits from Isis' applib's FixtureScripts service).
* Fixture setup methods in EstatioAdministrationService now moved to EstatioFixtureScripts
* Existing fixtures converted either to CompositeFixtureScript or SimpleFixtureScript.
* updated EstatioSystemInitializer for the integration tests.

In addition:
* fixed "Migration" appearing as a menu more than once (due to ApiItaly vs Api services)