Bug 188052 Enhance the behavior of DimensionConditionHandle
Current in model implementation, there could be multiple DimensionConditionHandle corresponding to one dimension. This will cause problem for both UI and DtE. What we expect is that for each dimension, there are only one DimensionConditionHandle accompany with. Model should merge all the duplicate DimensionConditionHandle so that when UI/DtE is using model API the we can get unique DimensionConditionHandle for each dimension.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/olap/TabularCubeHandle.java
{
	/**
	 * Constructs a handle for the given design and design element. The
	 * application generally does not create handles directly. Instead, it uses
	 * one of the navigation methods available on other element handles.
	 * 
	 * @param module
	 *            the module
	 * @param element
	 *            the model representation of the element
	 */
	public TabularCubeHandle( Module module, DesignElement element )
	{
		super( module, element );
	}
	/**
	 * Returns the data set of this cube.
	 * 
	 * @return the handle to the data set
	 */
	public DataSetHandle getDataSet( )
	{
		return (DataSetHandle) getElementProperty( DATA_SET_PROP );
	}
	/**
	 * Sets the data set of this cube.
	 *