i18n exercises

Some of my early work in i18n-ing the exercise utility files.

You can read about my general progress here:
https://docs.google.com/a/khanacademy.org/document/d/1pAgslsND2t4ltKlqMMNP4PCkDtvkcyJ_VlsvqFDkFCA/edit

And my effort to hardcode in all plural usage:
https://docs.google.com/a/khanacademy.org/spreadsheet/ccc?key=0ApubWHv0aMirdGp6dzBweVR3NHJ6alFJck9ucFRDbkE#gid=0