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/elements/structures/DimensionCondition.java
/**
	 * Gets the primary key list for this dimension condition.
	 * 
	 * @return the primary key list if set, otherwise null
	 */
	public List getPrimaryKeys( )
	{
		return primaryKeys;
	}
	/* (non-Javadoc)
	 * @see java.lang.Object#clone()
	 */
	protected Object clone( ) throws CloneNotSupportedException
	{
		DimensionCondition struct = (DimensionCondition) super.clone( );
		if ( primaryKeys != null )
		{
			struct.primaryKeys = new ArrayList();
			for ( int i = 0; i < primaryKeys.size( ); i++ )
			{
				struct.primaryKeys.add( primaryKeys.get( i ) );
			}			
		}
		struct.hierarchy = (ElementRefValue) ( hierarchy == null ? null : hierarchy.copy( ) );
		return struct;
	}
	
	
}