Test and build squads

Now that we have a reason to use our entire roster we need a better way to build squads. Currently the only way to use the squad builder is if there's an arena or GW fight left. But if all are completed there's no way to access the build function.

It would be excellent if we had a) access to the squad builder from a menu option, and b) if we had a generic arena we could fight battles in against an AI team, like a practice arena without a time limit but instead endless waves of enemy and an end button.

thanks