Date Formats

- Fixed broken documentation for custom report definitions regarding column
  formats.
- Modified date access to use the more efficient Date::get_date method, which
  also shrinks the code.
- Added the 'remaining' format for all date columns.

src/columns/ColDue.cpp

@@ -42,8 +42,6 @@ ColumnDue::ColumnDue ()
   _name      = "due";
   _label     = STRING_COLUMN_LABEL_DUE;
 
-  _styles.push_back ("countdown");
-
   Date now;
   now += 125;
   _examples.push_back (Duration (now - Date ()).formatCompact ());