Tournaments: support showing users who have joined
Tournaments: support showing users who have joined

During signups in elimination tournaments, show the number of users who
have joined in place of the empty bracket

asgdf/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,panpawn/Gold-Client,panpawn/Gold-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,panpawn/Gold-Client,sirDonovan/Pokemon-Showdown-Client