TranslateTask added

Hi Chase. I've reached a decent milestone with the TranslateTask. I updated the documentation so hopefully it's all clear. I tried not to touch your existing classes very much.

Some non-obvious consequences of my changes:
- okapi-ant now requires Okapi 0.24-SNAPSHOT
- okapi-ant now targets Java 1.7

I didn't know what you wanted to do about the version, so I left it 1.0.0.

Let me know if you have any questions or concerns.