- Added exi capability utilities, handlers and necessary modifications

- Added exi capability utilities, handlers and necessary modifications
- Exi parameters decomposition
- Introduced HandlerManipulator class in netconf-api to be used for
  handlers management on channel pipeline
- Exi encoding/decoding test added
- exi returns NetconfMessage
- added DOM attributes
- exi encode decode test to expect NetconfMessage instead of Document
- XmlElement.getName() returns localName first and tagName if localName not present, incorporated notes from Robert
- NetconfSession implements all common methods
- added copyright where needed
- ProtocolMessageEncoder/Decoder stored in session and replaced with Exi
  enc/dec
- exi encoder/decoder interface become comaptible with
  ProtocoleMessageEncoder/Decoder and no longer needs to be taken care of
  this handlers
- created thirdParty bundle for exi
- incorporation of Maros's notes

Author:    Martin Bobak <mbobak@cisco.com>
Signed-off-by: Martin Bobak <mbobak@cisco.com>
Change-Id: If9f20cef34ec05495eb212f6a584dd65a401dc0a
Signed-off-by: Martin Bobak <mbobak@cisco.com>