EventData now has a generic data type
Added the PelixFuture type, a Runnable to be used in threads

It allows to set a result-typed method to execute, and a method to call
back in case of success or error.
Added a utility method Target.toUids(Collection<Peer>)

Due to type erasure, we can't have both Target(Collection<Peer>) and
Target(Collection<String>) constructor, hence this method to convert a
collection of Peer objects to a collection of UID Strings
Implementation of the HTTP sending part

Based on Jabsorb for serialization (the Python part must be updated)
Added generic type to EventData objects used in Herald Core