Bug 213671 Expose evaluate() method in IReportContext
Need Engine expose evaluate() method in IReportContext interface, this will be used to evaluate global Javascript expression in case there's no resultset bound to current report item.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/script/internal/ReportContextImpl.java
{
	protected ExecutionContext context;
	public ReportContextImpl( ExecutionContext context )
	{