Display software licenses in the UI

[TheAssassin]

Some of our components actually require us to provide the licenses in the binaries. We don't do that right now, and should fix it.

In my opinion, there's two viable options: A CLI parameter (AppImageLauncher --appimagelauncher-licenses), or integrating with the [?] button proposed in https://github.com/TheAssassin/AppImageLauncher/issues/83#issue-360135964, containing information on the used components and their license texts.

[azubieta]

Actually, I guess that we should have a "copyright view" to show the AppImage license and if required the licenses of the modules included. But it would mean that our users will have to do one click more before deploying or running an AppImage

[TheAssassin]

It's enough to provide some "slightly hidden" message box containing the information. As long as it's available from the UI, it's all fine.