Don't show developer options to secondary users

Show just a message that developer options are not available for the user.

Also fix silent exit of AddAccount operation by showing a toast that user
cannot add accounts.

Bug: 7409523
Bug: 8519646
Bug: 7304007

Change-Id: Id3f430d568d6b7151ac55f86dbc0ef91803fa10c

src/com/android/settings/accounts/ManageAccountsSettings.java

@@ -332,6 +332,7 @@ public class ManageAccountsSettings extends AccountPreferenceBase
                 getPreferenceScreen().addPreference(preference);
                 if (mFirstAccount == null) {
                     mFirstAccount = account;
+                    getActivity().invalidateOptionsMenu();
                 }
             }
         }