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/EnumEntity.js

@@ -1,5 +1,11 @@
+import Grammar from "../serialization/Grammar.js"
 import SymbolEntity from "./SymbolEntity.js"
 
 export default class EnumEntity extends SymbolEntity {
 
+    static grammar = this.createGrammar()
+
+    static createGrammar() {
+        return Grammar.symbol.map(v => new this(v))
+    }
 }