pom.xml: Bumped version to 3.1.0-SNAPSHOT

Monitor.java: Added support for sending exams when they have been completed, instead of requiring a report.
Worker.java: Fixed names for "retrieve-timeout-in-secs" and "fail-on-incomplete-study" flags.

Monitor.java: Switched to using exam status constants from Exam.java.
Monitor.java: Added support for automatically retrying failed jobs.