removed the deprecated usage of include
removed the deprecated usage of include

added on_delete parameter

changes made as suggested

updated the courses wiki url to use include

updated the wiki urls

made changes as suggested

cpennington/edx-platform,arbrandes/edx-platform,msegado/edx-platform,cpennington/edx-platform,edx-solutions/edx-platform,angelapper/edx-platform,appsembler/edx-platform,edx-solutions/edx-platform,stvstnfrd/edx-platform,arbrandes/edx-platform,mitocw/edx-platform,mitocw/edx-platform,eduNEXT/edunext-platform,eduNEXT/edunext-platform,EDUlib/edx-platform,cpennington/edx-platform,arbrandes/edx-platform,appsembler/edx-platform,EDUlib/edx-platform,mitocw/edx-platform,eduNEXT/edunext-platform,msegado/edx-platform,edx/edx-platform,angelapper/edx-platform,msegado/edx-platform,angelapper/edx-platform,stvstnfrd/edx-platform,stvstnfrd/edx-platform,cpennington/edx-platform,arbrandes/edx-platform,appsembler/edx-platform,eduNEXT/edx-platform,angelapper/edx-platform,eduNEXT/edx-platform,EDUlib/edx-platform,edx/edx-platform,edx/edx-platform,eduNEXT/edx-platform,msegado/edx-platform,edx/edx-platform,mitocw/edx-platform,edx-solutions/edx-platform,eduNEXT/edx-platform,edx-solutions/edx-platform,eduNEXT/edunext-platform,stvstnfrd/edx-platform,msegado/edx-platform,appsembler/edx-platform,EDUlib/edx-platform