Use main switcher activity, small improvements

- hosts EULA
- goto either setup or messages

app/src/main/java/eu/faircode/email/ActivitySetup.java

@@ -39,7 +39,7 @@ public class ActivitySetup extends ActivityBase implements FragmentManager.OnBac
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_setup);
 
-        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
+        getSupportActionBar().setDisplayHomeAsUpEnabled(false);
 
         getSupportFragmentManager().addOnBackStackChangedListener(this);