keywordType can't be edited in tree editor
Problem: space inserted before value of 'keywordType' attribute in XML tree
editor, which causes an invalid document.
To reproduce: open any EML2 document in the tree editor, click "Show attrs", and
then navigate to the keyword section. Add a keyword, and set "keywordType" to
"place". A space is inserted before "place". Delete the space, and then move to
another field, then move back to the keywrodType attribute. The space has now
returned before "place". Click "Finish" and you get an invalid document error.