These are much more complex than all qtype already supported
so I have been pretty hard on the existing code.
I could not figure out what mathematical functions need
to be converted from webct to PHP format. The only function
I have converted so far is the webct x**y that was converted to PHP pow(x,y)
Each format is now in it's own subdirectory, which allows the
format to have as many files as it likes. The formats are now
detected automatically (no need to edit lib.php anymore) and
the parent class is now in mod/quiz/format.php
Lastly, I added Paul Shew's new GIFT format.
