Bug 181121 Model should provide utility method for cube to get correspond dimension key.
In model cube handle, the relation of cube data set and dimension data sets are managed by a series of dimension condition handles.We need model to add utility method so that we can easily get corresponding dimension data set column names according to given cube dimension keys.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DimensionConditionHandle.java
* @param key
	 * @throws SemanticException
	 */
	public void removePrimaryKey(String key ) throws SemanticException
	{
		MemberHandle memberHandle = getMember( DimensionCondition.PRIMARY_KEYS_MEMBER );
		memberHandle.removeItem( key );
	}
	/**
	 * Gets the referred hierarchy handle of this condition.
	 * 
	 * @return hierarchy handle of this condition if found, otherwise null
	 */
	public HierarchyHandle getHierarchy( )
	{
		ElementRefValue refValue = (ElementRefValue) ( (Structure) getStructure( ) )
				.getLocalProperty( getModule( ),
						DimensionCondition.HIERARCHY_MEMBER );
		if ( refValue == null || !refValue.isResolved( ) )
			return null;
		DesignElement element = refValue.getElement( );
		return (HierarchyHandle) element.getHandle( element.getRoot( ) );
	}
	/**
	 * Gets the referred hierarchy name of this condition.
	 * 
	 * @return hierarchy name of this condition if set, otherwise null
	 */
	public String getHierarchyName( )
	{