Add a "Generate Random Port" button, beside port input field in docker-application settings

[Greyberry]

This would be a welcome addition and quality of life improvement.

Would be cool if it could avoid portnumbers that are already taken by another docker-application.

[Squid]

Not a bad idea.  Should be noted though that whenever installing anything via Apps, it does warn you if the default host ports conflict within another app already running.