Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/barryvdh/laravel-snappy/src/IlluminateSnappyPdf.php

@@ -0,0 +1,108 @@
+<?php namespace Barryvdh\Snappy;
+
+use Knp\Snappy\Pdf;
+use Illuminate\Filesystem\Filesystem;
+
+class IlluminateSnappyPdf extends Pdf {
+    /**
+     * @var \Illuminate\Filesystem\Filesystem
+     */
+	protected $fs;
+
+	/**
+	 * @param \Illuminate\Filesystem\Filesystem
+     * @param string $binary
+     * @param array $options
+	 */
+	public function __construct(Filesystem $fs, $binary, array $options, array $env)
+	{
+		parent::__construct($binary, $options, $env);
+
+		$this->fs = $fs;
+	}
+
+    /**
+     * Wrapper for the "file_get_contents" function
+     *
+     * @param string $filename
+     *
+     * @return string
+     */
+    protected function getFileContents($filename)
+    {
+        return $this->fs->get($filename);
+    }
+
+    /**
+     * Wrapper for the "file_exists" function
+     *
+     * @param string $filename
+     *
+     * @return boolean
+     */
+    protected function fileExists($filename)
+    {
+        return $this->fs->exists($filename);
+    }
+
+    /**
+     * Wrapper for the "is_file" method
+     *
+     * @param string $filename
+     *
+     * @return boolean
+     */
+    protected function isFile($filename)
+    {
+        return strlen($filename) <= PHP_MAXPATHLEN && $this->fs->isFile($filename);
+    }
+
+    /**
+     * Wrapper for the "filesize" function
+     *
+     * @param string $filename
+     *
+     * @return integer or FALSE on failure
+     */
+    protected function filesize($filename)
+    {
+        return $this->fs->size($filename);
+    }
+
+    /**
+     * Wrapper for the "unlink" function
+     *
+     * @param string $filename
+     *
+     * @return boolean
+     */
+    protected function unlink($filename)
+    {
+        return $this->fs->delete($filename);
+    }
+
+    /**
+     * Wrapper for the "is_dir" function
+     *
+     * @param string $filename
+     *
+     * @return boolean
+     */
+    protected function isDir($filename)
+    {
+        return $this->fs->isDirectory($filename);
+    }
+
+    /**
+     * Wrapper for the mkdir function
+     *
+     * @param string $pathname
+     *
+     * @return boolean
+     */
+    protected function mkdir($pathname)
+    {
+        return $this->fs->makeDirectory($pathname, 0777, true, true);
+    }
+   
+}