ScriptInterpreter: return result of the evaluation

The ScriptEngine#eval method returns a result. Let's pass it along.

Author: ctrueden

src/main/java/org/scijava/script/DefaultScriptInterpreter.java

@@ -83,10 +83,10 @@ public synchronized String walkHistory(final String currentCommand,
 	}
 
 	@Override
-	public void eval(final String command) throws ScriptException {
+	public Object eval(final String command) throws ScriptException {
 		if (history != null) history.add(command);
 		if (engine == null) throw new java.lang.IllegalArgumentException();
-		engine.eval(command);
+		return engine.eval(command);
 	}
 
 	@Override

src/main/java/org/scijava/script/ScriptInterpreter.java

@@ -65,9 +65,10 @@ public interface ScriptInterpreter {
 	 * Evaluates a command.
 	 * 
 	 * @param command the command to evaluate
+	 * @return result of the evaluation
 	 * @throws ScriptException
 	 */
-	void eval(String command) throws ScriptException;
+	Object eval(String command) throws ScriptException;
 
 	/**
 	 * Returns the associated {@link ScriptLanguage}.