Feature/sections tool sm2

This pull request contains changes for delete section" 
- added remove_section method that uses canvas_sdk
-prevent primary sections from being deleted
- added ajax call to UI to handle 
    *hide the deleted row on success
    * display success and failure message
    * display special message when primary section is attempted to deleted(even though UI doesn't have a delete for primary sections)
- unit tests
- UI has a 2 delete icons as placeholder -one for deletable sections and a disabled one when member count >0

The method name and comment are incorrect- I started off with a particular test case, but seem to have modified it without changing the descriptions. ALso, the remove_section should be there on line 1146. Essentially that method when corrected should be:
	
         @patch('add_people.views.render')
	@patch('add_people.views.sections.delete_section')
	@patch('add_people.views.logger.error')
	def test_remove_section_raises_exception_on_delete_section_returning_400(self, log_replacement, delete_section_replacement, render_replacement):
		""" Assert that when SDK method returns an error status code, an exception is raised """
		request = self.delete_section_stub()	
		delete_section_replacement.return_value.status_code = 400
		self.assertRaises(Exception, remove_section(request,request.section_id,request.sis_section_id))