Change orbat marker merging behaviour

[Freddo3000]

I'd like to change it so that markers only merge when there are more than a single child marker.

As an example, if there is only an Alpha squad, it should only merge into Alpha and not Platoon. If there is both and bravo and alpha squads, it should merge into platoon as normal.

This is mostly an issue with low player counts where there are limited elements.