fixed issue with circular dependence on disjoint box-box computation;
based on relevant changes in develop branch
Merge branch 'feature/relate' of github.com:mkaravel/geometry into feature/relate

Conflicts:
	include/boost/geometry/algorithms/detail/overlay/get_turns.hpp
added custom turn comparison functors
added helper function to print turns
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops
implementation of follower for linear geometries;
added test files for difference of linear geometries;
added copyright headers
current implementation for difference of linear geometries (still a prototype);
added some copyright headers and made minor fixes;
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops
fixed the result of a test case
changes in code for linear-linear geometries difference
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops
added a couple more test cases
added code that removes duplicate turns;
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops
Merge branch 'develop' of https://github.com/boostorg/geometry into feature/setops
added support for the LS/MLS difference; need to add tests as well
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops
rearranged and simplified test code for differences of linear geometries;
added test cases for the LS/MLS difference;
polished debug macros a bit;
re-arranged code so that linestrings are not transformed to multilinestrings;
added implementations for all four pairs of LS/MLS combinations;
added unit tests that were missing for new combinations;