Use YUI's DragDrop delegates for course dragdrop, rather than initialising a Drag object for each individual section and each individual activity/resource. Also, clone a single drag handle for activities/resources, rather than repeatedly creating a whole new one with the same parameters for each activity/resource.
Initially, the default section title was swapped within the course format
javascript functions. Though some section titles may be custom and does not
require swapping, in addition they may have links to single section view. This
introduces some callback functions for define what needs to be done in
sections libs and js files.
Using topics format as default is not a great idea, as we can end up
half-working dragdrop for some formats. With the current soiution, drag-drop
will not work for format, unless required js functions have been created in
format.js
It allows to define M.course.format.swap_sections and
M.course.format.get_section_selector in the course format javascript file, so
that course dragdrop is aware about perculiar layout and changes that need to
be done when sections are swapped.
