adds firebase connection and notifications

- notification handler pushes background and
  foreground notifications to the phone directly
- firebase connection pushes remote notifications
  in background and foreground
- firebase unique token currently logged only, should
  be send directly to server via rest

app/src/main/res/layout/fragment_first.xml

@@ -4,7 +4,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    tools:context="com.example.bump.ui.FirstFragment">
+    tools:context="com.maenle.bump.ui.FirstFragment">
 
     <TextView
         android:id="@+id/textview_first"