A whole bunch of classes/interfaces/exceptions added, many refacturings:

A whole bunch of classes/interfaces/exceptions added, many refacturings:
- New classes for "tag support" added. Tags can be the "object types" this hub
  is going to share. But the purpose is kept somewhere generic so other purposes
  may come.
- A way lot interfaces updated and added (sorry for lame description)
- New factories added: (read full description way down)
  + The SocketDiscoveryFactory creates singleton instances for socket discovery
  + The PackageDiscoveryFactory does the same for package recipient discovery
  + The RecipientListFactory creates instances for recipient lists
  + The PackageTagsFactory creates singleton instances for package tags
- New class RecipientList added which can be used for tracking recipients and
  iterated on.
- New discovery classes added: ("Resolver" may also be fine naming these classes)
  + The PackageSocketDiscovery tries to "discover" the correct socket resource
    depending on the package's tags. Well, mostly this will be TCP, but UDP
    should not be forgotten... ;-)
  + The PackageRecipientDiscovery tries to "discover" the correct recipient
    based on the 'recipient' entry in the package data. May sound not obvious
    but there are some recipients which are no session id and/or IP:port
    combination. A good example is 'upper' which is an alias for all upper
    nodes like bootstrap, master and list nodes are.
- New ObjectTypeRegistry added. This registry does hold a list of all valid
  and therefore "shareable" object types in an XML. For example 'announcement'
  should only be shared with the 'upper' nodes, and only spreaded once.
- New (required for above registry) ObjectRegistryTemplateEngine added to handle
  the object_registry.xml file.
- Announcement descriptor updated
- TODOs.txt/README updated