Make visibility status more visible

[jidanni]

We choose go to first waypoint. Nothing happens*.

We chose go to beginning of GPX track. Nothing happens*.

What's going on?

Oh! We didn't notice we had turned off the layer's visibility!

It's so hard to tell. The symbol is very unobvious. You have to look for a tiny little broken eyeball slash.

And on the menu to the right there ought to be a giant red warning in the background saying, "Hey Holmes, you haven't turned on the visibility of this layer. Most anything you choose in this menu won't make much sense to you."

(*Depending on background you might see some movement.)