Add in overrides to getValueAsString/setValueFromString so string settings make sense (#448)

This was probably arguably an oversight on my part last time I went near this code.
Sorry!

Co-authored-by: 20kdc <asdd2808@gmail.com>

src/main/java/me/zeroeightsix/kami/setting/impl/StringSetting.java

@@ -22,4 +22,13 @@ public class StringSetting extends Setting<String> {
         return converter;
     }
 
+    @Override
+    public String getValueAsString() {
+        return getValue();
+    }
+
+    @Override
+    public void setValueFromString(String s) {
+        setValue(s);
+    }
 }