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/Basic4/46_ReadHtml.php

@@ -0,0 +1,19 @@
+<?php
+
+// Turn off error reporting
+error_reporting(0);
+
+use PhpOffice\PhpSpreadsheet\IOFactory;
+
+require __DIR__ . '/../Header.php';
+
+$html = __DIR__ . '/../templates/46readHtml.html';
+$callStartTime = microtime(true);
+
+$objReader = IOFactory::createReader('Html');
+$objPHPExcel = $objReader->load($html);
+
+$helper->logRead('Html', $html, $callStartTime);
+
+// Save
+$helper->write($objPHPExcel, __FILE__);