#139 Escape secuences aren't supported with XML

[Alberto Saez Torres]

HAPI can't support the normalized expression of escape secuences in XML

The "XML_Encoding_Rules_for_HL7_v2_Messages" document define at 2.7.8.1 point than ER7 escape secuences should be expressed as:
<escape V="__escape_secuence___"/>

As:

\H\ Should be expressed as <escape V="H"/>
\N\ Should be expressed as <escape V="N"/>
\.br\ .... <escape V=".br"/>
\.spn\ .... <escape V=".spn"/>
\.in±n\.... <escape V=".in±n"/>
\.ti±n\ .... <escape V=".ti±n"/>

But, HAPI:

* When generating XML, creates the ER7 form (\.br\, \H\, etc..)
* When parsing XML, can't understand this syntax, and cant

This is related to the artifact ID 1239414:
https://sourceforge.net/tracker/index.php?func=detail&aid=1239414&group_id=38899&atid=423835

[Alberto Saez Torres]

Java test program to read and parse XML escape characters

[Christian Ohr]

see e.g. http://www.hl7.org/Special/committees/xml/drafts/v2xml1mlbb.pdf

[Christian Ohr]

Added required functionality. May need some cleanup though.