[distance] Do not use cartesian default strategy for non-cartesian Pt/Box and Box/Box
[distance] Add preliminary version of Pt/Box spherical strategy.
[strategies] Add move course() to algorithms/detail and use it in spherical side and distance strategies.
[distance] Optimize cross_track_point_box - calculate courses only once, do not use other strategies than PP
[distance] Fix compilation error in get_comparable<> specialization for distance_cross_track_point_box<>
[distance][strategy] (spherical) Cosmetic changes - comment, lines length.
Merge pull request #132 from awulkiew/fix/distance_spherical

Fix/distance spherical