[jx8fb] Adding the Facebook SDK to Android Studio project

Steps followed to add Facebook SDK libraries to JX8 AS project

1. Edit the build.gradle file adding the dependency on FBSDK
   Added the line:
   implementation 'com.facebook.android:facebook-android-sdk:[4,5)'
2. Open Android Studio and let it build the JX8 project
3. ---19 errors building resource XML files
   :-( it should work as said by Facebook, but it is not true
4. ...now trying to find "a solution"...
   1. Installing... Android SDK Build-Tools 27.0.3 (revision: 27.0.3)
   2. Changed build.gradle to target SdkVersion 26 (instead of 23)
   3. Removed unused imports in MainActivity.java
      e.g. import android.support.v7.internal.view.menu.MenuBuilder;
5. Now, the project build w/o errors