Make judge return the full results.

Most uses of codegolf are going to want to know more than whether the
submission passes or not.  They'll want to be able to display to the
user the full details about what their program output and what the
sample program output, what the exit status was, etc.
Add constant to the execute results.
Add stderr to response from docker script execution.

PHP was sending errors to stdout rather than stderr.  This fixes that,
and sends stderr back in the response so that the user can get access to
it.