i18n, "Change Password" menu toggle

Starting from the pull request of sgonzaloc (#34), I added internationalization to a few spots he missed, and also enabled internationalization of the user-facing accounts-base and accounts-password error messages (see i18n/de_DE.js for German examples).

The language can be changed with
```
i18n.setLanguage('de_DE');
```
on the client.

I also removed a toggleDropdown() call that was closing the dropdown menu immediately after clicking the "Change Password" button.

Thanks for all the work you are putting into this package!