Update dependencies, rework UI file

[bugaevc]

Seeing that my #100 finally got merged, I thought to try doing more improvements & modernizations.

This is what it looks like:

I'm not at all sure that you should merge this as is, particularly the dependency on master SDK may be unacceptable.

[bertob]

Hooray for toning down the grid :tada:

What's up with the raised undo/redo buttons though?

[bugaevc]

What's up with the raised undo/redo buttons though?

I thought that was intentional, it's coming from the linked CSS class. (Dunno why it doesn't show up in main.) I can drop linked if you'd like that.

[bertob]

Yeah, I wouldn't link these :+1:

[bugaevc]

Done