Add small tutorial

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Account Importer (Android Library Project)

How to use it?

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1) you'll need to extend **IAccountImport**

That means that you have to implement the following method:

    public void accountAccessGranted(OwnCloudAccount account);

As you can see in the following example, it's really easy to get the account data

    @Override

    public void accountAccessGranted(OwnCloudAccount account) {

        mUsernameView.setText(account.getUsername());

        mPasswordView.setText(account.getPassword());

        mOc_root_path_View.setText(account.getUrl());

    }

And then you can call the dialog with the following code:

    public static void show(FragmentActivity activity, IAccountImport accountImport)

Here a small example:

    view.findViewById(R.id.btn_importAccount).setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View view) {

            ImportAccountsDialogFragment.show(getActivity(), LoginDialogFragment.this);

        }

    });

    //If no other accounts (from other apps) are available.. hide the button

    if(AccountImporter.findAccounts(getActivity()).size() <= 0) {

        view.findViewById(R.id.btn_importAccount).setVisibility(View.GONE);

    }

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