Improve quality of coalescing-as-needed; add options to limit feature count (#25)

* Add an option to limit geometry vertex count

* Update docs and changelog

* Track desired feature count and geometry size in strategies

* Remove dead code for a long-forgotten inaccessible option

* Fix the option name in changelog

* Refine coalesce-smallest to only coalesce onto other small features

* Clean polygons before coalescing-as-needed

* Don't accumulate tiny polygon holes as negative dust

* Add the option not to limit the feature count at maxzoom

* Add options to limit feature count more abruptly in each tile

* Revert "Add the option not to limit the feature count at maxzoom"

This reverts commit ace173ab7a.

* Revert "Fix the option name in changelog"

This reverts commit 38dbce8405.

* Revert "Add an option to limit geometry vertex count"

This reverts commit d379fdf06b.

* Remove test for reverted option

* Remove more leftovers from geometry size limiting

* Update changelog

tile.hpp

@@ -44,15 +44,17 @@ struct strategy {
 	size_t coalesced_as_needed = 0;
 	size_t detail_reduced = 0;
 	size_t tile_size = 0;
+	size_t feature_count = 0;
 	size_t tiny_polygons = 0;
 
-	strategy(const atomic_strategy &s, size_t ts) {
+	strategy(const atomic_strategy &s, size_t ts, size_t fc) {
 		dropped_by_rate = s.dropped_by_rate;
 		dropped_by_gamma = s.dropped_by_gamma;
 		dropped_as_needed = s.dropped_as_needed;
 		coalesced_as_needed = s.coalesced_as_needed;
 		detail_reduced = s.detail_reduced;
 		tile_size = ts;
+		feature_count = fc;
 		tiny_polygons = s.tiny_polygons;
 	}