Modify Change tune handling. Change all change notes to reference the filename of the tune to change to. Modify web and document generators to pull the change note out of the abc and generate an appropiate bit of content. This is now, in both cases, a hyperlink. In the process, remove the tune-specific .tex facility. It wasn't being used. I could really do with a proper templating system, and using some sort of templating in the LaTeX generation.