Reorganize Samples

The samples have become unwieldy when running them from a browser. In particular, the drop-down lists are fixed size with no scrolling, and many of them are now just too large. I have moved all the Calculation samples up a level, and broken several categories (Basic, Chart, DateTime, Engineering, Financial, and Reader) into several pieces.

Convert-Online (now found in the Engineering category) had a number of different problems which are now resolved. It is the only member with any significant code change.

samples/Basic2/20_Read_Excel2003XML.php

@@ -0,0 +1,13 @@
+<?php
+
+use PhpOffice\PhpSpreadsheet\IOFactory;
+
+require __DIR__ . '/../Header.php';
+
+$filename = __DIR__ . '/../templates/excel2003.xml';
+$callStartTime = microtime(true);
+$spreadsheet = IOFactory::load($filename);
+$helper->logRead('Xml', $filename, $callStartTime);
+
+// Save
+$helper->write($spreadsheet, __FILE__);