Add the ability to hide request sharing when raising an issue from the customer portal

I am building out our service desk and noticed that when customers in our service desk portal that are members of a single organization report an issue the shared with section was defaulting to the organization. In my search to remove this option, I came across the link below which is closed but did not address all of the concerns.

https://jira.atlassian.com/browse/JSDCLOUD-4382

This solves a piece of the problem in that it allows you to change the default behavior for all organizations in your service desk. However, this leaves 2 problems that haven't been addressed and were called in the previously linked request as not being addressed.

1. You can only control this globally instead of at the org level. There's not enough flexibility in how this was initially addressed
2. There's no way to disable sharing at the portal screen. This is another missed requirement/suggestion that was in the previous request. 

I personally would use #2 above, and there were a few others that wanted #1 implemented in the previous request.