Patch adds csv export functionality in course reports: outline, participation and statistics.

I did not use new downloads methods from refactored tablelib.php (MDL-14187). I did not have it in my moodle instance (ver. 1.9.5) and I wanted to be some how more economical in code changes adding this feature. So I have just added new method print_csv() to table class and use it similarly to some other exports found in app.

Export in participation report depends on my _ user profile fields in export_ improvement (CONTRIB-2395), but if some does not want profile fields in this export just skip hunks marked by [mod201009281545] in diff file.