WIP: group management ready to be debugged

...-windows/TournamentManager.csproj.CoreCompileInputs.cache

...0-windows/TournamentManager.csproj.GenerateResource.cache

...0-windows/TournamentManager.csprojAssemblyReference.cache

obj/Debug/net5.0-windows/TournamentManager.dll

obj/Debug/net5.0-windows/TournamentManager.pdb

obj/Debug/net5.0-windows/ref/TournamentManager.dll

obj/TournamentManager.csproj.nuget.dgspec.json

obj/TournamentManager.csproj.nuget.g.props

obj/project.assets.json

obj/project.nuget.cache

obj/rider.project.restore.info

src/GroupControl.Designer.cs

src/GroupControl.cs

src/GroupSelectedEventArgs.cs

src/ManageTournamentForm.cs

src/Match.cs

src/MatchSelectedEventArgs.cs

src/OpponentsSelectedEventArgs.cs