Split grammar (#15)

* Move grammar parsers to entity classes

* Fix includes

* Fix Entity5 test

* Small detail

* Fix unknown keys entities

* Persistent grammar objects

* Fix grammar

* Grammar from variable

js/entity/NaturalNumberEntity.js

@@ -1,8 +1,15 @@
+import Grammar from "../serialization/Grammar.js"
 import IntegerEntity from "./IntegerEntity.js"
 import Utility from "../Utility.js"
 
 export default class NaturalNumberEntity extends IntegerEntity {
 
+    static grammar = this.createGrammar()
+
+    static createGrammar() {
+        return Grammar.naturalNumber.map(v => new this(v))
+    }
+
     constructor(values = 0) {
         super(values)
         this.value = Math.round(Utility.clamp(this.value, 0))