When specifying required assignment files, the instructor must be able to specify the file type extension: eg, ".h", ".c", ".zip", etc. The instructor must also be able to mark the file as a text file or not. (Perhaps a separate option, dependent on that being selected, is to display it in the review page.)
Then, backend, the files should actually be saved in that format. Currently files are all saved as .txt, except for a hack to make ZIP files work as was required in Spring semester 2009.
Instructor may specify extension. TODO: engine needs to check if text-based or not when actually displaying it on the review page. Could just check for known text extensions (txt, h, cpp, c, cs, java)
Currently known text file extensions are checked to determine if it's a text file.