Add config flag for disabling option to "Clear Schedule"

I.e. when editing the schedule

tailbone/templates/shifts/schedule_edit.mako

@@ -8,6 +8,7 @@
 
     $(function() {
 
+        % if allow_clear:
         $('.clear-schedule').click(function() {
             if (confirm("This will remove all shifts from the schedule you're " +
                         "currently viewing.\n\nAre you sure you wish to do this?")) {
@@ -16,6 +17,7 @@
                 $('#clear-schedule-form').submit();
             }
         });
+        % endif
 
         $('#copy-week').datepicker({
             dateFormat: 'mm/dd/yy'
@@ -88,7 +90,9 @@
   <div class="buttons">
     <button type="button" class="save-changes" disabled="disabled">Save Changes</button>
     <button type="button" class="undo-changes" disabled="disabled">Undo Changes</button>
+    % if allow_clear:
     <button type="button" class="clear-schedule">Clear Schedule</button>
+    % endif
     <button type="button" class="copy-schedule">Copy Schedule From...</button>
   </div>
 </%def>
@@ -98,10 +102,12 @@ ${self.timesheet_wrapper(with_edit_form=True)}
 
 ${edit_tools()}
 
+% if allow_clear:
 ${h.form(url('schedule.edit'), id="clear-schedule-form")}
 ${h.csrf_token(request)}
 ${h.hidden('clear-schedule', value='clear')}
 ${h.end_form()}
+% endif
 
 <div id="day-editor" style="display: none;">
   <div class="shifts"></div>

tailbone/views/shifts/schedule.py

@@ -121,6 +121,8 @@ class ScheduleView(TimeSheetView):
 
         context['form'] = form
         context['page_title'] = "Edit Schedule"
+        context['allow_clear'] = self.rattail_config.getbool('tailbone', 'schedule.allow_clear',
+                                                             default=True)
         return self.render_full(**context)
 
     def clear_schedule(self):