ISIS-783: further improvements to IntegrationTest framework

1. automatic injection of services into tests (allowing @Inject on fields of services)
2. after fixtures installed, commit tran and start a new session.  This ensures that any objects are loaded from objectstore / DB.

In addition, updates to quickstart (todo) app:
3. using @Inject for services
4. now using ClockService in integ tests
5. split out the setup of fixtures vs other setup tasks.
ISIS-783: further minor improvements to integtest framework

* IntegrationTestAbstract#nextSession(), to supplement nextTransaction(); causes a new Isis/DataNucleus session (ie clear caches)
* IsisSystemForTest new openSession and closeSession
* ScenarioExecution new openSession and closeSesssion
* ScenarioExecution#injectServicesInto support @javax.inject.Inject for fields.