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
}
	/**
	 * Returns the list index pointed to by this reference.
	 * <p>
	 * property.member.list[ <strong>n </strong> ][.member] <br>
	 * 
	 * property.list[ <strong>n </strong>][.member] <br>
	 * property.list[n].member.list[ <strong>n </strong>][.member]
	 * 
	 * @return the list index pointed to by this reference
	 */
	public int getIndex( )
	{
		if ( propDefn.isList( ) )
			return index[depth - 1];
		return index[0];
	}
	/**
	 * Returns the depth of the reference: 1 or 2.
	 * <p>
	 * property.list[n][.member] --&gt 1 <br>
	 * property.member[.list[n]]
	 * 
	 * property.list[n].member.list[n][.member] --&gt 2
	 * property.member.list[n].member property.member.member
	 * 
	 * @return the depth of the reference
	 */
	public int getDepth( )
	{