Clear up some confusion about attribute count and external references

Now the count is always adjacent to whereever the key/value pair is
stored, and is not kept in the serial feature object other than as
the length of the vectors of keys and values.

geocsv.cpp

@@ -108,7 +108,6 @@ void parse_geocsv(std::vector<struct serialization_state> &sst, std::string fnam
 		sf.t = 1;  // POINT
 		sf.full_keys = full_keys;
 		sf.full_values = full_values;
-		sf.m = sf.full_values.size();
 
 		serialize_feature(&sst[0], sf);
 	}