Jump to the corresponding anchor after adding / editing an activity

When you add or edit an activity you get redirected to the top of the corresponding section after saving. As activities are added at the end of the section, this means a lot of scrolling, if you add some activities in a row.

I'd suggest to redirect the user to the anchor #module-... after updating / adding a new activity, so there is a smooth workflow when editing the course.

Adding this to modedit.php would be easy, but as courseformat_base::get_view_url() already uses the anchor in the URL for choosing the section on singlepage formats it might be necessary to implement a solution for MDL-75542 first.