fixes #4 "Implicit vs. explicit mappings":

- changed signature of Scope.hasMapping(Class) to isSpecified(*)
  - is true when specify() or map() where used
+ public property Scope.implicitResolving
  - expects a ProviderStrategy that should be used for implicit resolving
  - as get/optionally expect a Class as parameter, the implementation of ImplicitResolvingStrategy is pretty simple
  - this stuff will get more complex when we allow to resolve identities
  - after success the Provider is not persisted, so this has no impact on isSpecified()