Add citation to quotes

I wanted to be able to list a citation (source of the quote) with the quotes. I've added another field to the quotes table to hold it. Then I added another field to the input form.

While I was at it, I added a new link on the display after adding a quote to add another quote.

I made one small change on the settings form for the "quotes leader" description text: "i.e." means "that is." I believe you meant "for example," which is "e.g."

I have never tried an import, so I'm not certain that I have correctly modified those routines.

I also changed the quotes.install code for the new field (including update_5 to add it). I made one small change to the uninstall code as well, to delete blocks belonging to quotes.