dataHandlerNumeric::getString always format the number as a double

the getString(const imbxUint32 index) in the dataHandlerNumeric class returns always a double value. The function is not considering the type of the template. This is a problem if class is templated with e.g. imbxUint16, when e.g. VR = US, SS etc.

The problem can be fixed with the following line of code

convStream << std::fixed << (((dataHandlerType*)m_pMemoryString)[index]);