Add a new option to set an initial value for an attribute in each feature (#115)

* Starting on --set-attributes

* Add a JSON form to accumulate-attribute

* Fix formatting

* Set attributes, JSON form

* Also handle setting attributes to unquoted values

* Factoring out character-mangling in the names of tests

* Rename tests for new quoting convention

* Test for JSON form of attribute setting

* Test for JSON form of attribute accumulation

* Forgot to increment the version

main.hpp

@@ -5,8 +5,10 @@
 #include <atomic>
 #include <string>
 #include <vector>
+#include <map>
 
 #include "json_logger.hpp"
+#include "serial.hpp"
 
 struct index {
 	long long start = 0;
@@ -58,6 +60,7 @@ extern std::string attribute_for_id;
 extern int tiny_polygon_size;
 extern size_t limit_tile_feature_count;
 extern size_t limit_tile_feature_count_at_maxzoom;
+extern std::map<std::string, serial_val> set_attributes;
 
 struct order_field {
 	std::string name;