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
* Date -> BigDecimal
	 * 		Date.getTime();
	 * String -> BigDecimal
	 * 		new BigDecimal(String);
	 * @param source
	 * @return
	 * @throws BirtException
	 */
	public static BigDecimal toBigDecimal( Object source ) throws BirtException
	{
		if ( source == null )
			return null;
		if ( source instanceof BigDecimal )
		{
			return (BigDecimal) source;
		}
		else if ( source instanceof Number )
		{
			 
			
			
			
			String str = ( (Number) source ).toString( );
			try
			{
				return new BigDecimal( str );
			}
			catch ( NumberFormatException e )
			{
				throw new BirtException( pluginId,