Bug 153896 Improve the performance of BIRT datetime-converting
The current datetime converting algorithm in birt.core, xml&flatfile ODA implementations are not efficient enough.This is because we use java's SimpleDateTimeFormatter to parse ISO8601 compatible date/time values. We should write our own datatime string parser for ISO8601 datetime format.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/DataTypeUtil.java
* Above conversion can be done without error, but obviously
	 * the result is not right. This method will do such a simple check,
	 * in DateFormat.SHORT case instead of all cases.
	 * 		Year is not lower than 0.
	 * 		Month is from 1 to 12.
	 * 		Day is from 1 to 31.  
	 * @param source
	 * @param locale
	 * @return Date
	 * @throws BirtException
	 */
	public static Date toDateWithCheck( String source, ULocale locale )
			throws BirtException
	{
		DateFormat dateFormat = DateFormatHolder.getDateInstance( DateFormat.SHORT,
				locale );
		Date resultDate = null;
		try
		{
			resultDate = dateFormat.parse( source );
		}
		catch ( ParseException e )
		{
			return toDate( source, locale );
		}
		
		if ( DateUtil.checkValid( dateFormat, source ) == false )
		{
			throw new BirtException( pluginId,
					ResourceConstants.CONVERT_FAILS,