CMS7-5867: use new artifact ID and version of hippo commons

CMS7-5876: try to explain the annotation mechanism with methods that are named differently
 
 Any method name will suffice if the annotation is present.  The HippoEventListener is a convenience / conventional interface.

CMS7-5884: use new dependencies

CMS7-5884: copy for tag hippo-services-parent-1-alpha

CMS7-5884: use new dependencies

CMS7-5878 added improved annotation scanning : instead of looping through all superclasses, we now only loop through the methods of the current class, and then check per method whether there is a Subscribe annotation on the method, or on the method of one of its super classes, or one of its interfaces (or superclass interfaces). Added extensive unit tests for all kinds of combinations

CMS7-16  ignore files

CMS7-5873: create a cross-context api for event listeners

The guava library does not offer an api for listeners, while we do need one for
the cross-context services.  The Subscribe (method marker) annotation was
forked to accomplish this.

For the eventbus implementation, that does use guava, the annotation finder was
forked to locate the new annotation.

CMS7-5873: introducing the singleton annotation

If this annotation is present on an interface, no name needs to be specified
when registering or retrieving a service.  Otherwise, the name _is_ necessary.

CMS7-5873: create initial folder structure for services project