New/Customizable way to load data

[alexy.pellegrini]

@alexy.pellegrini

It would be possible to get rid of the iostream base (and make an adaptor if needed), and not splitting the resource and the stream, I did this because I followed the stream/streambuf approach but it is not necessary.

As discussed, I got rid of the standard streams for the base implementation, and made an adaptor to std::istream for smoother transition.
An MR has been done on KWSys: https://gitlab.kitware.com/utils/kwsys/-/merge_requests/264