Improve loadFromStream

[scheibel]

E.g., by bypassing C++ std::getline and use the more C-like interface std::strtod (example: https://github.com/cginternals/unifiedmemory-demo/blob/master/source/unifiedmemory/Computation.cpp#L216).
The trade-off is the missing error handling, which you lack nonetheless.
Further, the parsed data point can be moved to the target row.