Bug 179737 The MeasureHandle should be able to provide data type info
We are now allow user input expression as measure expression. However this brings difficulties in determine the data type of a measure expression evaluation result. We need MeasureHandle to be enhanced to include the data type info. Please note that data type "any" is not accepted.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/elements/interfaces/IMeasureModel.java
{
	/**
	 * Name of the property that defines the function to apply on measure
	 * element.
	 */
	static final String FUNCTION_PROP = "function"; 
	/**
	 * Name of the property. If the isCalculated is false, then the value of
	 * this property should be a column name. If it is true, the value of this
	 * property should be an expression for the computed measure.
	 */
	static final String MEASURE_EXPRESSION_PROP = "measureExpression"; 
	/**
	 * Name of the property that indicate whether this measure is computed by
	 * other measures.
	 */
	static final String IS_CALCULATED_PROP = "isCalculated"; 
}