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/Reader2/20_Reader_worksheet_hyperlink_image.php

@@ -0,0 +1,61 @@
+<?php
+
+use PhpOffice\PhpSpreadsheet\Shared\File;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+
+require __DIR__ . '/../Header.php';
+$inputFileType = 'Xlsx';
+
+$helper->log('Start');
+
+$spreadsheet = new Spreadsheet();
+
+$aSheet = $spreadsheet->getActiveSheet();
+
+$gdImage = @imagecreatetruecolor(120, 20);
+if ($gdImage === false) {
+    throw new Exception('imagecreatetruecolor failed');
+}
+$textColor = imagecolorallocate($gdImage, 255, 255, 255);
+if ($textColor === false) {
+    throw new Exception('imagecolorallocate failed');
+}
+imagestring($gdImage, 1, 5, 5, 'Created with PhpSpreadsheet', $textColor);
+
+$baseUrl = 'https://phpspreadsheet.readthedocs.io';
+
+$drawing = new PhpOffice\PhpSpreadsheet\Worksheet\MemoryDrawing();
+$drawing->setName('In-Memory image 1');
+$drawing->setDescription('In-Memory image 1');
+$drawing->setCoordinates('A1');
+$drawing->setImageResource($gdImage);
+$drawing->setRenderingFunction(
+    PhpOffice\PhpSpreadsheet\Worksheet\MemoryDrawing::RENDERING_JPEG
+);
+$drawing->setMimeType(PhpOffice\PhpSpreadsheet\Worksheet\MemoryDrawing::MIMETYPE_DEFAULT);
+$drawing->setHeight(36);
+$helper->log('Write image');
+
+$hyperLink = new PhpOffice\PhpSpreadsheet\Cell\Hyperlink($baseUrl, 'test image');
+$drawing->setHyperlink($hyperLink);
+$helper->log('Write link: ' . $baseUrl);
+
+$drawing->setWorksheet($aSheet);
+
+$filename = File::temporaryFilename();
+
+$writer = PhpOffice\PhpSpreadsheet\IOFactory::createWriter($spreadsheet, $inputFileType);
+$writer->save($filename);
+
+$reader = PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);
+
+$reloadedSpreadsheet = $reader->load($filename);
+unlink($filename);
+
+$helper->log('reloaded Spreadsheet');
+
+foreach ($reloadedSpreadsheet->getActiveSheet()->getDrawingCollection() as $pDrawing) {
+    $helper->log('Read link: ' . ($pDrawing->getHyperlink()?->getUrl() ?? 'none'));
+}
+
+$helper->log('end');