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

main.hpp

@@ -43,6 +43,7 @@ extern int quiet_progress;
 extern json_logger logger;
 extern double progress_interval;
 extern std::atomic<double> last_progress;
+extern int extra_detail;
 
 extern size_t CPUS;
 extern size_t TEMP_FILES;
@@ -51,6 +52,19 @@ extern size_t max_tile_size;
 extern size_t max_tile_features;
 extern int cluster_distance;
 extern std::string attribute_for_id;
+extern int tiny_polygon_size;
+
+struct order_field {
+	std::string name;
+	bool descending;
+
+	order_field(std::string _name, bool _descending)
+	    : name(_name),
+	      descending(_descending) {
+	}
+};
+
+extern std::vector<order_field> order_by;
 
 int mkstemp_cloexec(char *name);
 FILE *fopen_oflag(const char *name, const char *mode, int oflag);