v3.3 - Update Readme, fix cleanup bug, flip button CSS.

-v3.3.
-Update README.md.
  -Remove mention of Docker repo, as it is not maintained.
  -I appreciate all of the community feedback at #46.
  -I will come up with an official Docker solution.
-Fix bug in cleanFiles() function that was causing problems with archive conversions & preventing cleanup.
-Flip button CSS, so buttons don't appear quite so... upside-down... all the time.
-Remove un-needed (redundant) button related CSS from HRConvert2.css.
-Increase default DeleteThreshold in config.php from 30 to 60 minutes.
-Remove un-needed extension being passed to the convertDrawings() function.
-Fix drawings not returning a valid filename.
  -Conversions would complete, but not download.
-Tested ImageMagick support for SVG, could not get it to work.
-Tested Dia support for converting things into PNG, BMP, and JPG. Got PNG to work, so added support.

Author: zelon88

versionInfo.php

@@ -1,7 +1,7 @@
 <?php
 // / -----------------------------------------------------------------------------------
 // / APPLICATION INFORMATION ...
-// / HRConvert2, Copyright on 10/30/2023 by Justin Grimes, www.github.com/zelon88
+// / HRConvert2, Copyright on 3/5/2024 by Justin Grimes, www.github.com/zelon88
 // /
 // / LICENSE INFORMATION ...
 // / This project is protected by the GNU GPLv3 Open-Source license.
@@ -12,7 +12,7 @@
 // / on a server for users of any web browser without authentication.
 // /
 // / FILE INFORMATION ...
-// / v3.2.9.
+// / v3.3.
 // / This file contains the current HRConvert2 version for update verification purposes.
 // /
 // / HARDWARE REQUIREMENTS ...
@@ -30,5 +30,5 @@
 
 // / -----------------------------------------------------------------------------------
 // / The version of this HRConvert2 installation.
-$Version = 'v3.2.9';
+$Version = 'v3.3';
 // / -----------------------------------------------------------------------------------