reverted addition of #include in this file
'
removed inclusion of dispatch/distance.hpp
multi/algorithms/distance.hpp now include algorithms/distance.hpp;
reverted this file to its previous state (same as develop branch)
replaced inclusion of geometry.hpp by specific includes;
re-implemented distance using the existing dispatch mechanism;
moved dispatches to individual files;
dispatch/distance.hpp contains only the generic dispatch definition;
remaining problem: inclusion of implementation details is currently done after the definition of the distance free functions;