[strategies][length] make the default length result variant aware
[algorithms][length] change length return type to default_length_result<...>::type
[algorithms][perimeter] change perimeter return type to default_length_result<...>::type
Add projected_point_ax cartesian distance strategy.
[strategies] Remove inconsistent (and for now not needed) operators in projected_point_ax_result
[strategies] projected_point_ax strategy relocated to separate file
[strategies] Add douglas_peucker version taking LessCompare
[strategies] Add less-comparator for projected_point_ax result in detail::douglas_peucker
[simplify] fix double, replaced by template parameter
[simplify] prepare test for distance object instead of always value, and
added overload accepting a strategy
[simplify] prepare for other simplify strategy: added testcase
[simplify][test] added test with strategy
[simplify][test] splitted tests such that test with strategy does not
test the version without strategy, to avoid mixing strategy types
[simplify] prepare for Adam's enhanced douglas_peucker with pull request #89
[buffer] move simplify call to separate function to apply using ax-strategy
[strategies] Fix projected_point_ax+douglass_peucker compilation errors.

Add again operator< for projected_point_ax_result needed to compare the distance with 0 (explicitly converted into the same type).
Remove template parameter from projected_point_ax_less::operator().
Add tests for simplify() and detail::simplify_insert().
[strategies] Modify handling of 0-length segments in projected_point_ax.

For 0-length segments assume that the segment is perpendicular to the Pt->ProjPt vector.
In other words ATD = 0.
[simplify] add zigzag testcase for testing adt/xdt
Merge branch 'develop' into feature/projected_point
[strategies] Add more robust check in projected_point_ax_less