corrected compilation bugs on windows using visual 2010

Compilation bug and warning correction:
- isinf() and isnan() were defined as macros for windows build in GRTCommon.h, but used prefixed with "std::": I removed the prefixes and added "using namespace std;" at the beginning of the file.
- GRT::MLBase::saveModelToFile() and GRT::MLBase::loadModelToFile() were both declared with a const string parameter, but some of the overloadings in the derived classes were declared with non-const parameter: because the parameter was a copy and not a reference, I chose to remove the const qualifier.
- I corrected some other issues about double to uint conversion.