Bug 145022 Provide a utility method to help GUI enhance aggregate on.
DtE will provide a method hasAggregation(String expression) in org.eclipse.birt.core.data.ExpressionUtil, and the return value will be true when the expression is a valid JS expression and it has aggregation defined.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/ExpressionUtil.java
* @param operator
	 * @return
	 */
	private static boolean isValidProceeding( char operator )
	{
		if ( ( operator >= 'A' && operator <= 'Z' )
				|| ( operator >= 'a' && operator <= 'z' ) || operator == '_' )
			return false;
		return true;
	}
}
/**
 * A utility class for internal use only.
 * 
 */
class ParseIndicator
{
	private int retrieveSize;
	private int newIndex;
	private boolean isCandidateKey;
	private boolean omitNextQuote;
	private boolean candidateKey1;
	private boolean candidateKey2;
	ParseIndicator( int retrieveSize, int newIndex, boolean isCandidateKey,
			boolean omitNextQuote, boolean candidateKey1, boolean candidateKey2 )
	{
		this.retrieveSize = retrieveSize;
		this.newIndex = newIndex;
		this.isCandidateKey = isCandidateKey;
		this.omitNextQuote = omitNextQuote;