ini support for update script and 7th guest mt32/sc55 fixes

[nanner55]

This adds ini file support for user options to the updater script. I use /media/usb0 and wanted to avoid having to change the script when it's updated. Looks like you are probably already working on this so feel to delete this pull request or only use it as a reference.

Also, 7th Guest MT32 and SC55 configuration files (groovie.ini) required minor changes to work. Let me know if I should separate them from the update script changes in another pull request.

There are some script bug fixes which are noted in the commit messages.

[flynnsbit]

Can you just verify I got all of your changes into the main branch? I was in the middle of moving things around so I had to manually merge.

[nanner55]

All of my changes are included in your main branch and it works great. A few things I forgot to mention in the original pull comment:

• The optional ini file takes the same prefix name as the top-level script that is invoked and sits along side it in /media/fat/Scripts/. So it would currently be at: /media/fat/Scripts/AO486_Update_Top300_Pack.ini. Both update.sh and update_all.sh use this same approach and I borrowed some code from them.
• The format of the ini file is the same as the user options listed at the top of the updater script. Any options not in the ini file use defaults in the updater script so any new options added should work as intended without changing the ini. Since both the top-level and updater script source it, it's also possible to put the top-level script options in the ini file for debug. For example, to test my changes I added SCRIPT_URL="..." to my local ini file and temporarily pointed it at my cloned repo on github.
• The user options were renamed and capitalized to be more consistent with the update_all.sh script and ini that many people use. This way it's easier for someone to integrate it in the future. Several names had to change to avoid conflicts with the sourced ini options. I generally don't like to modify the coding convention in other people's code, but it seemed useful here. One thing the update_all.sh people will need to be careful is of the longer script file name. They use ps and awk to extract the script name for sourcing the ini. But the options they use on ps truncate the process name to 16 characters which results in the wrong ini file name.

Also, thanks for all your work on the pack and updates to it.