Hide/Unhide decks on Deck Selection mode

[GinoGalotti]

After #68 you can Hide/Unhide decks when you select the scenario.

That's not happening if you select different decks from the Deck tab. I don't know if many people are using that workflow, but it might be nice to make it consistent.

It would be also nice if we hide the Attack modifier deck as well. Right now, in order to hide it, the user has to untick "Show Modifier deck" on the deck tab, we could add the option on the top of the page like the rest.

[GrandVizierOlaf]

I've fixed this in my fork, but it includes other changes as well. I'll see about isolating them and making a PR soon.