Move enumerations to outer scope

[ErikSchierboom]

Currently, all code is compiled in a single DLL. This caused some namespacing issues, which could be solves by moving enumeration declarations within a class. An example of this is the go-counting exercise:

public class GoCounting
{
    public enum Player
    {
        None,
        Black,
        White
    }

With the #199 PR being worked on, each exercise will have its own solution. The namespacing workaround mentioned above is no longer necessary, so we can (and should) move the inner types to the outer namespace:

public enum Player
{
    None,
    Black,
    White
}

public class GoCounting
{
}

Note: this requires #199 to be merged before we can continue.