Added two improvements, the first at Ray's request, and the other because it makes sense:

• The popup message that shows the lemma and reading for categorization now shows two versions of each, one with the wrapping tags and one without. This involved an improvement to the utility function which spits out a dom node in XML code, making it recursive.
• When loading a Collate file, the app now pops up an input dialog asking for the xml:id of the poem. This is safer than leaving it to the user, because it's easy to forget to add the correct id.