Escape the nodeValue with htmlspecialchars()

Fixes ISLANDORA-879 :
  https://jira.duraspace.org/browse/ISLANDORA-879
Merge remote-tracking branch 'nigelgbanks/7.x-fix-for-autocomplete-notice' into lyr-master

Fixes "Notice: Undefined index: \#autocomplete_path in theme_textfield()"
https://github.com/nigelgbanks/islandora_xml_forms/commit/05bc4d06d90b0c795b4f06bf4f0da8989146582d
Merge pull request #96 from lyrasis/lyr-master

Escape the nodeValue with htmlspecialchars()