ISIS-597: use ServicesInjectorDefault to wire services prior to postconstruct

In addition, currently the DomainObjectContainer is built lazily, much later on,
by the PersistenceMechanism.  There doesn't really seem to be any good
reason for this.  So, moving this responsibility earlier.

In addition, since IsisSessionFactoryDefault did nothing other than delegate to
its superclass, IsisSessionFactoryAbstract, have collapsed this hierarchy.
ISIS-597: minor tidy up in unit test
ISIS-597: now runs ok

with services injected prior to @PostConstruct
ISIS-598: can now use @Inject on field...

... for dependency injection