Legacy XMLNode removal

The work in progress for the subject is available as a brach in svn:

http://svn.igniterealtime.org/svn/repos/xiff/branches/xml-migration

Feel free to test and give feedback, patches etc. Any help would be appreciated.

This will make the library smaller in file size and easier to read.

Related issue: http://www.igniterealtime.org/issues/browse/XIFF-32