spec tests for instance caching strategies

+ ResolverAdapter.usingInstanceCaching()/expectingCachedInstance
+ ResolverInstanceCachingStrategies with test for resolving a specified type
   tested for Scope.map() in ScopeMapInstanceCachingStrategies
consistent naming

- replaced "defined" -> "specified", "defines" -> "specifies"
- improved wording in some places
spec tests for instance caching strategies

- BaseResolverSpec
  ~ setUpResolver() is now final
  ~ calls assertRelaxedResolver when necessary
  + additionalSetUp() can be overridden to extend the setup

+ ResolverInstanceCreation.extendedAsserts(identifier)
  - allows additional asserts for all tests, to avoid a lot of duplicate code
~ RelaxedResolverInstanceCreation deleted
  + (Relaxed)ResolverInstanceCreationWithInstanceCaching
  + (Relaxed)ResolverInstanceCreationWithoutInstanceCaching
    are extending (Relaxed)ResolverInstanceCreation and overriding extendedAsserts()
~ ScopeMapInstanceCreation extends RelaxedResolverInstanceCreationWithoutInstanceCaching
  - as it is the default behaviour
+ ScopeMapInstanceCreationAsSingleton, ScopeMapInstanceCreationAsEagerSingleton
  - both extend RelaxedResolverInstanceCreationWithInstanceCaching

sorry for refactorings and new tests in one commit, but this way it was so easy