FELIX-4112 Add meta-annotations for handler description

* @HandlerBinding can be used to declare an annotation as a handler
  annotation (will produce Elements in the metadata structure). The
  supporting annotation type do not have to be in a package containing
  'handler' or 'ipojo'
* @Ignore can be used to ignore an annotation that would be (otherwise)
  mapped to a custom handler annotation (because it contains 'handler'
  or 'ipojo' in its name)
* Unified support for @Stereotype, @HandlerBinding and @Ignore
* Merged BindingRegistry and AnnotationBindingRegistry into 1 entity
** Implementation is split into 3 delegating registries for better
   separation of concerns
* Module DSL improved to support @Stereotype, @HandlerBinding and
  @Ignore registration
* Added annotations javadoc


git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1507289 13f79535-47bb-0310-9956-ffa450edef68