refactored out xml components into multiple files

ts/docx/xml-components/default-attributes.ts

@@ -0,0 +1,29 @@
+import {BaseXmlComponent} from "./base";
+
+export abstract class XmlAttributeComponent extends BaseXmlComponent {
+    protected root: Object;
+    private xmlKeys: Object;
+
+    constructor(xmlKeys: Object, properties: Object) {
+        super("_attr");
+        this.xmlKeys = xmlKeys;
+
+        this.root = properties
+
+        if (!properties) {
+            this.root = {};
+        }
+    }
+
+    replaceKey(): void {
+        if (this.root !== undefined) {
+            _.forOwn(this.root, (value, key) => {
+                var newKey = this.xmlKeys[key];
+                this.root[newKey] = value;
+                delete this.root[key];
+            });
+            this[this.rootKey] = this.root;
+            delete this.root;
+        }
+    }
+}