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

mbtiles.cpp

@@ -372,6 +372,12 @@ std::string stringify_strategies(std::vector<strategy> const &strategies) {
 			any = true;
 		}
 
+		if (strategies[i].feature_count > 0) {
+			state.json_write_string("feature_count_desired");
+			state.json_write_number(strategies[i].feature_count);
+			any = true;
+		}
+
 		state.json_end_hash();
 	}
 	state.json_end_array();