Revision 562

- created macros/IO.pl, which is loaded with no opmask by PG.pm. It is a copy
  of WeBWorK::PG::IO.pm, with some changes to make it work as a macro package.
  The translator no longer shares IO.pm's functions with the safe compartment.
  This is a BAD THING, and should be reconsidered when the Translator is
  revised.
- Changed many (but not all) checks for HTML or HTML_tth modes to match /^HTML/
  in the macros.
- changed &header to &head in Problem.pm
- Added problem environment variables for gif2eps and png2eps and modified
  &dangerousMacros::alias to use them
- fixed MOST of the harmless warnings in the system. there's still the "Use
  of uninitialized value in null operation" warning in template(), tho.

Still to come:

- make images in PDFs work
- fix TTH mode character encodings on mac (maybe)
- have logout button invalidate key
- Pretty die messages (from outside of the translator)
- Feedback - need nice modular way of sending email
- Options - email address and password