Hiding By Default UX

[Malkierian]

When this was added, the functionality of listening to everything on every mapping edit ended up causing problems sometimes when the active controller would be hidden by default (as can happen automatically with the bug where multiple devices for the same controller get added after disconnects) because you can click a mapping that's shown, hit a button on your controller, and have that mapping disappear because it's overwriting the visible one and the one you created isn't visible. When editing existing mappings, the re-map should only respond to the device the original mapping belonged to. And perhaps a message should show up saying you're trying to map inputs with a device that it doesn't belong to? Or figure out some way of automatically showing the mappings for a device that is hidden by default?

[briaguya-ai]

as of #793 mappings are just "SDL mappings" instead of specific physical device mappings - so we don't have giant lines with mappings for every connected device, and therefore don't need to do any hiding by default (hiding isn't a thing as of that PR)