Postionless algorithms -- C++ prototypes

We want to have an implementation of positionless algorithms and a translation from C++ iterators to positionless, so that we can use positionless with STL algorithms.

Positionless features

TODO

Translation from iterators

TODO

Building & testing

cmake -D CMAKE_BUILD_TYPE=Release -G Ninja -S . -B .build
cmake --build .build
ctest --test-dir .build