Implement command router

[FiniteReality]

Somehow commands need to be routed to the correct location so they can be handled.

I could possibly use the previous structures defined in 0.2, but they weren't necessarily the best...

[FiniteReality]

Currently this is done as part of the command parser in ab0e75c

[FiniteReality]

Since there are multiple ways to route a command (e.g. in Discord, each command has a unique identifier) this might be better to implement as part of the command store, and transition it to a semi-tree based structure

[FiniteReality]

The command store now uses a semi-tree based structure

[FiniteReality]

ICommandBinder can be used to bind an ICommand to a context, which in effect does the routing:

var binder = services.GetRequiredService<ICommandBinder>();

foreach (var command in potentialCommands)
{
    if (binder.TryBind(context, command))
    {
        context.Command = command;
        return
    }
}