Handling function for generating reports.
Requires the admin_forum permission.
Loads the Reports template and language files.
Decides which type of report to generate, if this isn't passed
through the querystring it will set the report_type sub-template to
force the user to choose which type.
When generating a report chooses which sub_template to use.
Depends on the cal_enabled setting, and many of the other cal_
settings.
Will call the relevant report generation function.
If generating report will call finishTables before returning.
Accessed through ?action=admin;area=reports.