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
String msg = context.getDesign( ).getMessage( key, locale );
		if ( msg == null )
			return "";
		return MessageFormat.format( msg, params );
	}
	public String getParameterDisplayText( String name )
	{
		return context.getParameterDisplayText( name );
	}
	public void setParameterDisplayText( String name, String displayText )
	{
		context.setParameterDisplayText( name, displayText );
	}
	
	public int getTaskType()
	{
		IEngineTask task = context.getEngineTask( );
		if ( task != null )
		{
			return task.getTaskType( );
		}
		return IEngineTask.TASK_UNKNOWN;
	}
	
	public ReportDesignHandle getDesignHandle( )
	{
		return (ReportDesignHandle) getReportRunnable( ).getDesignHandle( );
	}
}