Bug 179674 Support time dimension in model
When define time dimension in model, the "itTime" property will be set. However this is not enough. We also need to know to what precision the time value should be evaluated, say, year, month, day, etc. Model needs to be enhanced to support such requirement.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/olap/LevelHandle.java
* 
	 * @return iterator of static values
	 */
	public Iterator staticValuesIterator( )
	{
		PropertyHandle propHandle = getPropertyHandle( STATIC_VALUES_PROP );
		assert propHandle != null;
		return propHandle.iterator( );
	}
	/**
	 * Sets the base of the interval property of this level.IntervalBase, in
	 * conjunction with Interval and IntervalRange, determines how data is
	 * divided into levels.
	 * 
	 * @param intervalBase
	 *            interval base property value.
	 * @throws SemanticException
	 *             if the property is locked.
	 */
	public void setIntervalBase( String intervalBase ) throws SemanticException
	{
		setStringProperty( INTERVAL_BASE_PROP, intervalBase );
	}
	/**
	 * Return the interval base property value of this level.
	 * 
	 * @return interval baseF property value of this level.
	 */
	public String getIntervalBase( )
	{