1.0.23

Potentially disruptive change:

Logging has been changed from a hard dependency on log4j to using the slf4j framework which lets you choose your logging implementation at runtime. Depending on your application's runtime environment, you may have to add the following dependency to your project:

    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.27</version>
    </dependency>

For details see #111

Other changes:

• Ability to query Assignment Submission objects from courses and sections
• New field in ExternalTool model to indicate LTI version number
• New field in Assignment model for omitting an assignment from the final grade
• Several compiler/javadoc warning cleanups