Add a new editor for LoanItem

    * Separate LoanItemEditor from SalesQuoteItemEditor for simplicity
    * Bônus: clean some old an dusty code from Mesozoic Era (it was a great
      archeology found indeed). This code turn on and off extra information on a
      glade file when necessary but is not used anymore.

Change-Id: I28d7f8c3e1d5d92b93864c0258b6431e8a764699