[ADF-1549] Added files for Core library (#2345)

* [ADF-1549] Added files for Core library

* [ADF-1549] Updated md files following checks

docs/alfresco-api.service.md

@@ -0,0 +1,45 @@
+# Alfresco Api Service
+
+Provides access to initialized **AlfrescoJSApi** instance.
+
+<!-- markdown-toc start - Don't edit this section.  npm run toc to generate it-->
+
+<!-- toc -->
+
+- [Basic Usage](#basic-usage)
+- [Details](#details)
+
+<!-- tocstop -->
+
+<!-- markdown-toc end -->
+
+## Basic Usage
+
+```ts
+export class MyComponent implements OnInit {
+
+    constructor(private apiService: AlfrescoApiService) {   
+    }
+
+    ngOnInit() {
+        let nodeId = 'some-node-id';
+        let params = {};
+        this.apiService.getInstance().nodes
+            .getNodeChildren(nodeId, params)
+            .then(result => console.log(result));
+    }
+}
+```
+
+## Details
+
+**Note for developers**: _the TypeScript declaration files for Alfresco JS API
+are still under development and some Alfresco APIs may not be accessed
+via your favourite IDE's intellisense or TypeScript compiler. 
+In case of any TypeScript type check errors you can still call any supported 
+Alfresco JS api by casting the instance to `any` type like the following:_
+
+```ts
+let api: any = this.apiService.getInstance();
+api.nodes.addNode('-root-', body, {});
+```