Further cleanups to eval code in preparation for interactive tasks.
Review Request #213 - Created June 23, 2012 and submitted
- Fixed error handling for various methods such as chmod, which would have raised PHP warnings and killed the eval. - Replace previous hack with exceptions whenever judging a job needed to be interrupted due to an error. Replaced all log_error and log_assert with calls to eval_assert, which raises a EvalSystemError on failed assertion. - Got rid of task parameters in the grader code. Parameters are now merged into the $task object. - Linting fixes. - Fix site crash when mbstring extension not present.