Bug 189706 Enhance computed column aggregation function handling in UI.
Due to the issue discussed in 189705, current computed column aggregation builder in data set editor has bugs to extend: 1.When new a computed column, the aggregation argument field cannot be correctly set. 2.The argument field cannot be correct grayed out when user select a aggregation function without arguments 3.The available aggregation function list is incomprehensive 4.Some aggregation function cannot be set to model(say, weightedAve).
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ComputedColumnHelper.java
{
		assert resultClass != null;
		
		
		List cmptList = new ArrayList( );
		for ( int i = 0; i < ccList.size( ); i++ )
		{
			IComputedColumn cmptdColumn = (IComputedColumn) ccList.get( i );
			int cmptdColumnIdx = resultClass.getFieldIndex( cmptdColumn.getName( ) );
			
			
			if ( cmptdColumnIdx >= 1
					&& resultClass.isCustomField( cmptdColumnIdx ) )
				cmptList.add( new Integer( i ) );
			
			
		}
		int size = cmptList.size( );
		columnIndexArray = new int[size];
		computedColumn = new IComputedColumn[size];
		for ( int i = 0; i < size; i++ )
		{
			int pos = ( (Integer) cmptList.get( i ) ).intValue( );
			IComputedColumn cmptdColumn = (IComputedColumn) ccList.get( pos );
			computedColumn[i] = cmptdColumn;
			columnIndexArray[i] = resultClass.getFieldIndex( cmptdColumn.getName( ) );
		}
		isPrepared = true;
	}
}