Create a new `System` class

[dkrutsko]

Functions such as IsSys64Bit, IsAxEnabled and IsAdmin (as proposed by #41) belong in their own module, such as System. This class would probably be a static class and include other useful information about the system. One suggestion currently is to move the memory VM functions here as well. Although the functions in Memory would still be there since they are specialized to the process itself, specifically GetPtrSize and GetMaxAddress.