Changes to allow extending CalendarAdapter by clients

In my application I wanted to extend projects CalendarAdapter class in a CalendarAdapterExt class defined by my app. I wanted this class to have access to key members of the CalendarAdapter class. This patch makes these members protected in ExtendedCalendarView/src/com/tyczj/extendedcalendarview/CalendarAdapter.java.

In addition I need a ExtendedCalendarView.setAdapter method to allow setting a custom CalendarAdapter on the ExtendedCalendarView.