Turns out that magic "?" in the url was added by having a H.button in
the show controls/show sidebar/show tree in the top bar.

Also, fixed styling of "info" dropdown.

Now backend is set to Nothing before showing (it could be set to Just b
when clicking on "Login" in Home).

For other pages, tree needs space on the left.

Also, make components for the panelAction case expression.

This reverts commit 5b9aac47.