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

* [ADF-1549] Added files for Core library

* [ADF-1549] Updated md files following checks

docs/user-preferences.service.md

@@ -0,0 +1,61 @@
+# User Preferences Service
+
+Stores preferences for components.
+
+<!-- markdown-toc start - Don't edit this section.  npm run toc to generate it-->
+
+<!-- toc -->
+
+- [Details](#details)
+
+<!-- tocstop -->
+
+<!-- markdown-toc end -->
+
+## Details
+
+The preferences are bound to a particular `prefix` so the application can switch between different profiles on demand.
+
+For example upon login you can set the `prefix` as current username:
+
+```ts
+import { UserPreferencesService, AuthenticationService } from 'ng2-alfresco-core';
+
+@Component({...})
+class AppComponent {
+    constructor(private userPreferences: UserPreferencesService,
+                private authService: AuthenticationService) {
+    }
+
+    onLoggedIn() {
+        this.userPreferences.setStoragePrefix(
+            this.authService.getEcmUsername()
+        );
+    }
+}
+```
+
+As soon as you assign the storage prefix all settings that you get or set via the `UserPreferencesService` will be saved to dedicated profile.
+
+You can import the service in your controller and use its APIs like below:
+
+```ts
+@Component({...})
+class AppComponent {
+    constructor(userPreferences: UserPreferencesService) {
+
+        userPreferences.set('myProperty1', 'value1');
+        userPreferences.set('myProperty2', 'value2');
+
+        console.log(
+            userPreferences.get('myProperty1')
+        );
+    }
+}
+```
+
+The service also provides quick access to a set of the "known" properties used across ADF components.
+
+Known properties:
+
+- paginationSize (number) - gets or sets the preferred pagination size