Exclude NPCs from player statistics

src/main/java/net/therosegarden/playerstats/StatsStorage.java

@@ -9,6 +9,8 @@ interface StatsStorage extends Closeable {
 
     void save(PlayerRecord record) throws Exception;
 
+    void delete(UUID uuid) throws Exception;
+
     default void saveAll(Collection<PlayerRecord> records) throws Exception {
         for (PlayerRecord record : records) {
             save(record);