Require explicit opt-in for "clicking grid row checks box" feature

sometimes it makes sense *not* to enable that, in which case disabled
probably should be the default

tailbone/views/master.py

@@ -73,6 +73,10 @@ class MasterView(View):
     pageable = True
     checkboxes = False
 
+    # set to True to allow user to click "anywhere" in a row in order
+    # to toggle its checkbox
+    clicking_row_checks_box = False
+
     # set to True in order to encode search values as utf-8
     use_byte_string_filters = False
 
@@ -399,6 +403,7 @@ class MasterView(View):
             'url': lambda obj: self.get_action_url('view', obj),
             'checkboxes': checkboxes,
             'checked': self.checked,
+            'clicking_row_checks_box': self.clicking_row_checks_box,
             'assume_local_times': self.has_local_times,
         }
         if 'main_actions' not in kwargs and 'more_actions' not in kwargs: