Extra coordinate precision; feature ordering; compression improvements

* Add an option to retain extra coordinate precision at maxzoom

* Make sure not to shift away the extra detail from coordinates

* Add an option to convert double-precision attributes to single

* Sort attribute values in tiles to make them compress a little better

* Slightly improve polygon simplification

By choosing a point that would be retained after simplification
to be the start/end point that always gets retained

* I regret making all of these tests involve polygons

* Add an option to specify the size of tiny polygons

* Fix accidental requiring of argument for --single-precision

* Guard against duplicate points when generating "sizes" for them

* Restore the intended behavior that tiny polygons don't get simplified

* Make the extra detail settable rather than always maximizing it

* Revert "Improve maxzoom guessing for tightly-clustered point data sources (#4)"

This reverts commit fec5e8354c.

* Add an option to prevent choosing a base zoom higher than the maxzoom

* Keep the drop rate high enough when the basezoom gets constrained

* Revert "Revert "Improve maxzoom guessing for tightly-clustered point data sources (#4)""

This reverts commit db6bc27d9e.

* Add --order-by and --order-descending options

* Accept multiple --order-by and --order-descending-by sort keys

tile.hpp

@@ -25,13 +25,15 @@ struct atomic_strategy {
 	std::atomic<size_t> dropped_as_needed;
 	std::atomic<size_t> coalesced_as_needed;
 	std::atomic<size_t> detail_reduced;
+	std::atomic<size_t> tiny_polygons;
 
-	atomic_strategy() :
-		dropped_by_rate(0),
-		dropped_by_gamma(0),
-		dropped_as_needed(0),
-		coalesced_as_needed(0),
-		detail_reduced(0) {
+	atomic_strategy()
+	    : dropped_by_rate(0),
+	      dropped_by_gamma(0),
+	      dropped_as_needed(0),
+	      coalesced_as_needed(0),
+	      detail_reduced(0),
+	      tiny_polygons(0) {
 	}
 };
 
@@ -42,6 +44,7 @@ struct strategy {
 	size_t coalesced_as_needed = 0;
 	size_t detail_reduced = 0;
 	size_t tile_size = 0;
+	size_t tiny_polygons = 0;
 
 	strategy(const atomic_strategy &s, size_t ts) {
 		dropped_by_rate = s.dropped_by_rate;
@@ -50,6 +53,7 @@ struct strategy {
 		coalesced_as_needed = s.coalesced_as_needed;
 		detail_reduced = s.detail_reduced;
 		tile_size = ts;
+		tiny_polygons = s.tiny_polygons;
 	}
 
 	strategy() = default;