This change stores the list of columns that require text sorting in the session,
so the static function "get_sort_for_table" can work without any additional parameters.
This includes refactoring to extract methods like sort_icon and show_hide_link which I think makes the code easier to read.
Note also the change to make_styles_string that makes it usable with html_writer. (Perhpas we need a css_writer classe ;-))
You may think that the extra validation is unnecessary, since the sort fields are already validated when the URL parameters are parsed, however that overlooks an important point. There may be other options that affect which columns are in the SQL, for example the quiz show individual question grades setting. These other options can cause a column that was in the table, and being sorted on, to disappear. Therefore, it is necessary to re-validate the sort columns when they are used, to make sure they are still present, otherwise you can get ORDER BY sql that refers to non-existant columns, which then causes DB errors.
Note that this change removes ->reseturl, This was supposed to be a way to reset all the session stuff relating to a table automatically in some situations, but from using Moodle and reading the code, I don't beleive it was working. The code was horrible and not easily fixible, and has been broken for years, so I just removed it.
Major tasks undertaken in this patch:
* New format_text argument, overflowdiv.
* New page layout Report.
* Review of all format_text calls.
* Added support for the report layout to all themes.
* Changed forum post display from tables to divs.
Thanks very much to Remote Learner Canada, especially Hubert Chathi and Olav Jordan, for their work on the bulk of this code, and also Mike Churchward for supporting them. I worked on it after that (actually simplified it by removing a feature temporarily: multiple pages) to bring it more to what I was imagining, and to provide a base to build on and get all the navigation perfect.
There's still work to do. Some blocks don't quite work as expected, and some of the code still needs upgrading to bring it fully into line with 2.0. We also could use a much better course overview block and better CSS styling of the profile pages. But it's definitely more usable this it was, I think.
