Feature/disjoint

Major changes:
1) clean-up code;
2) move multi code to algorithms directory
3) updated segment-box algorithm that does not use numeric_limits
4) move bg::detail::equals::point_point implementation to proper place
5) add support for a few more geometry combinations (multi-point is not supported yet)
6) more compact dispatching by means of tag_cast
7) eliminate usage of segment_view