Enhance steam shortcut creation

[Lucki]

This fixes #319 by correcting the node which the game gets added to.
It also presets the vertical image cover if one is available.

I've also added that all tags are added to the shortcut in hope they'll create the corresponding collections inside steam automatically but this doesn't work yet. Although adding the game inside steam to a collection adds the tag to the shortcut in the file this doesn't work the other way around.

[tkashkin]

Thanks for your contributions.

I'll merge your PRs and finally push dev branch into master.
I've pushed refactoring branch, but it's still WIP and not very usable at the moment.

[Lucki]

I've pushed refactoring branch, but it's still WIP and not very usable at the moment.

That's quite a lot of changes :D
You want me to look into something or what's the reason behind publishing it already?

[tkashkin]

@Lucki I've pushed it just to be a bit more safe and to not accidentally lose any changes while merging. And to show that project is still alive.

You can see initial changes related to #304. Also some bugs may or may not have been fixed by rewriting.