All non shogun includes in header files shifted to corresponding .cpp for classifiers - A fix to issue #2557.

For this one, and the changes below (and possible others above). If you just have to change the include and everything compiles fine then there is something a bit funny. Why would the former include have been used? Also, you cannot rely on including CMath to make std math visible here. If CMath stops including std math then compilation of this file would break if it does depend on std math.