Add android books from google training (#2307)

* Add android books from google training

* Update free-programming-books.md

free-programming-books.md

@@ -712,6 +712,8 @@
 
 * [Agile Android Software Development](https://www.agiledroid.com) - Etienne Savard (PDF, epub, mobi)
 * [Android 4 App Development Essentials](http://www.techotopia.com/index.php/Android_4_App_Development_Essentials)
+* [Android Developer Fundamentals Course – Concepts](https://google-developer-training.gitbooks.io/android-developer-fundamentals-course-concepts/content/en/)
+* [Android Developer Fundamentals Course – Practicals](https://google-developer-training.gitbooks.io/android-developer-fundamentals-course-practicals/content/en/)
 * [Android Programming Guide for Beginners](http://eduonix.com/offers/Android_ebook_free_offer.html) (PDF - need email confirmation)
 * [Android Programming Succinctly, Syncfusion](https://www.syncfusion.com/resources/techportal/ebooks/android) ([PDF](https://www.syncfusion.com/Account/Logon?ReturnUrl=%2fresources%2ftechportal%2febooks%2fandroid), [Kindle](https://www.syncfusion.com/Account/Logon?ReturnUrl=%2fresources%2ftechportal%2febooks%2fandroid)) *(Just fill the fields with any values)*
 * [CodePath Android Cliffnotes](https://github.com/codepath/android_guides/wiki)