By Andrew Mills, Nidal al-Mughrabi, Ahmed Mohamed Hassan and Dan Williams DOHA/CAIRO/JERUSALEM (Reuters) – Israel and Hamas broadly agree in principle that an exchange of Israeli hostages for Palestinian prisoners could take place during a month-long ceasefire, but the framework plan is being held up by the two sides’ differences over how to bring a permanent end to the Gaza war, three sources said. Intense mediation efforts led by Qatar, Washington and Egypt in recent weeks have focused on a phased approach to release different categories of Israeli hostages – starting with civilians and endi…