Added generic overload method declarations for the ko.utils.arrayX funct...

I was missing some generic overloads for the ko.utils.arrayX functions. I had to explicitly type the arguments like so:

ko.utils.arrayForEach(this.bikes, (bike: Bike) => { bike.broken = true });

With this commit the type is implicit and typescript still knows the type:

ko.utils.arrayForEach(this.bikes, (bike) => { bike.broken = true });