BUG-625: convert DataPacketAdapter

This patch converts DataPacketAdapter from xtend to pure java. Same
level of functionality should be retained.

Change-Id: I72371da9bee9dd6b26851eb6c9635c0995e7ce97
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-625: convert DataPacketAdapter"