Move Packing related algorithms to Event/EventPacker

As preparation to change the output of the event packers from packed objects to packed data buffers, I move the PackedData and PackedDataBuffer to Event/EventPackers.

Event/EventPacker/dict/PackedEventDict.h

@@ -18,6 +18,8 @@
 #include "Event/PackedCaloDigit.h"
 #include "Event/PackedCaloHypo.h"
 #include "Event/PackedCluster.h"
+#include "Event/PackedData.h"
+#include "Event/PackedDataBuffer.h"
 #include "Event/PackedDecReport.h"
 #include "Event/PackedFlavourTag.h"
 #include "Event/PackedMCCaloHit.h"