libmath itself doesn't expose any stream operators anymore. However,
libutils is able to automatically print libmath types into its
io::ostream -- however matrices are not formatted nicely.
Added a new optional library, libmathio, that provides std::ostream
operators for all libmath types. libmathio does a better job at
formating matrices.
Also removed apply() and map() from libmath because there were not used
anywhere and they forced us to depend on <functional> in public headers.
