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

* [ADF-1549] Added files for Core library

* [ADF-1549] Updated md files following checks

docs/authentication.service.md

@@ -0,0 +1,48 @@
+# Authentication Service
+
+Provides authentication for use with the Login component.
+
+<!-- markdown-toc start - Don't edit this section.  npm run toc to generate it-->
+
+<!-- toc -->
+
+- [Basic Usage](#basic-usage)
+  * [Events](#events)
+- [Details](#details)
+
+<!-- tocstop -->
+
+<!-- markdown-toc end -->
+
+## Basic Usage
+
+**app.component.ts**
+
+```ts
+import { AuthenticationService } from 'ng2-alfresco-core';
+
+@Component({...})
+export class AppComponent {
+    constructor(authService: AuthenticationService) {
+        this.AuthenticationService.login('admin', 'admin').subscribe(
+            token => {
+                console.log(token);
+            },
+            error => {
+                console.log(error);
+            }
+        );
+    }
+}
+```
+
+### Events
+
+| Name | Description |
+| --- | --- |
+| onLogin | Raised when user logs in |
+| onLogout | Raised when user logs out |
+
+## Details
+
+The authentication service is used inside the [login component](../ng2-components/ng2-alfresco-login/README.md) and is possible to find there an example of how to use it.