Python 'review' test now properly inherits from ReviewTest
Python files now take variable values into total
Criteria files support specifying a grading group

Grading groups will be used to combine differently graded
parts of a given assignment.
Submit mode changes

If present, socrates adds a grading group to the dropbox path. In
addition, socrates now gives up if it cannot create directories in
the dropbox.
Changed order of pseudorandom dropbox path
Added umask to directory/file creation under dropbox

At BU, this will allow graders to submit grades in directories
with group & other read access. Assuming the dropbox directory is
not readable (but writable) and owned by the grading coordinator,
only the graders and coordinators can access the files.