<b> <hasicon> <icon>
The icon will be used by the branch.
<b> <hasicon> <none>
By default a branch has an icon, none overrides this default and effectively
disables the icon.
<l> <hasicon> <icon>
The icon will be used by the leaf.
<l> <hasicon> <none>
By default a leaf has an icon, none overrides this default and effectively
disables the icon.