Working ATB-sensitive active unit switching in battle

When I wired in the ATB timers, I made sure the UI would queue units who were ready but didn't have focus, so it ended up being fairly trivial to get available unit switching implemented (minus the standard Unity struggles, of course).

And while I didn't think to show it in this little demo, the battle menus do get focus correctly now. I think the biggest piece of the battle flow should be next: Getting single- and multi-unit targeting working in the UI and wiring up that logic on the server.

I haven't mitigated the ATB gauge delay yet, though I've started getting a server-client lag check in place to hopefully get it a lot closer to being accurate. I might punt on finishing that for now, though; I really want to get basic attack and maybe defend working.