Bug 139110 GUI enhancement to support create subquery more conveniently.
Description: GUI enhancement to support create subquery more conveniently. Steps to reproduce: Subquery means insert table/list inside another table/list item, and the inner table/list item doesn't has its own dataset binding. In latest build, if you want to creat a subquery structure, you have to use dataSetRow as binding expression for data items in inner table/list item. For example: 1. Insert a list, generate column data binding for it. 2. Add a group for the list. 3. Insert table to list group header which is used to display data rows in list group. Dont' bind table to dataset. 4. Insert a data to table detail row. 5. New a binding column for data, click to Open Expression Builder. The issue is that only "Availabel column bindings" is listed in Category but no "Available Data Sets". So I have to type dataSetRow[".."] by myself to generate correct subquery. For users, maybe they will mistakenly use "Available column bindings" which will generate expression like row._outer[".."] and get wrong result. So it is recommended to add "Available Data Sets" in Expression Builder for such case.
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
public static String resolveNull( String value )
	{
		return value == null ? "" : value; 
	}
	/**
	 * Converts the RGB object value to a String, the String format is "r,g,b",
	 * no quotation marks.
	 * 
	 * @param rgb
	 *            RGB value.
	 * @return String value.
	 */
	public static String getRGBText( RGB rgb )
	{
		if ( rgb != null )
		{
			return rgb.red + "," + rgb.green + "," + rgb.blue; 
		}
		return ""; 
	}
	/**
	 * Converts the String value to an RGB object value, the String format is
	 * "r,g,b", no quotation marks.
	 * 
	 * @param val
	 *            String value.
	 * @return RGB value.
	 */
	public static RGB getRGBValue( String val )
	{