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/core/MemberRef.java
* The property definition. Identifies the property.
	 */
	protected final ElementPropertyDefn propDefn;
	/**
	 * Array of two list indexes. Represents the ".list[n]" portion of the
	 * references.
	 */
	protected final int index[] = new int[2];
	/**
	 * Array of two member names. Represents the ".member" portion of the
	 * reference.
	 */
	protected final StructPropertyDefn member[] = new StructPropertyDefn[2];
	/**
	 * Number of list indexes: always 1 or 2.
	 */
	protected final int depth;
	/**
	 * Constructs one member reference as same as the given one.
	 * 
	 * @param memberRef
	 *            the member reference to copy
	 */
	MemberRef( MemberRef memberRef )
	{
		refType = memberRef.refType;
		propDefn = memberRef.propDefn;
		member[0] = memberRef.member[0];
		member[1] = memberRef.member[1];
		index[0] = memberRef.index[0];