Revision 1131

Made many changes:

- turned off PG warning catching in conf/global.conf.dist
- added warning reporting to conf/templates/ur.template (but not to
  other templates!)
- modified a couple of error messages in WeBWorK.pm
- made failure to create course environment and failure to find course
  directory fatal errors in WeBWorK.pm
- added warning queueing and call stack storing to Apache::WeBWorK
- added "warnings" and "if_warnings" template escapes to
  WeBWorK::ContentGenerator
- removed warning handling from WeBWorK::ContentGenerator::Problem
- code tidying in WeBWorK::ContentGenerator::Problem
- code tidying in WeBWorK::PG::ImageGenerator

-sam