SW-2430 OctoPrint Favicon is Shown in the Login Screen (#130)

* SW-2083 Change input field placeholder

* SW-2430 Change favicon for Login page

* SW-2083 Add new favicon SVG

src/octoprint/templates/login.jinja2

@@ -3,7 +3,7 @@
  <meta name="viewport" content="width=device-width,initial-scale=1">
  <title>OctoPrint Login</title>
 
- <link rel="shortcut icon" href="{{ url_for('static', filename='img/tentacle-32x32.png') }}">
+ <link rel="shortcut icon" href="{{ url_for('static', filename='img/favicon.svg') }}">
  <link rel="mask-icon" href="{{ url_for('static', filename='img/mask.svg') }}" color="#56BE37">
  <link rel="mask-icon-theme" href="{{ url_for('static', filename='img/mask-theme.svg') }}" color="#56BE37">
  <link rel="apple-touch-icon" sizes="114x114" href="{{ url_for('static', filename='img/apple-touch-icon-114x114.png') }}">
@@ -55,7 +55,7 @@
  {{ _('An account with the following permissions is required:') }} {{ permission_names|join(", ") }}
  </p>{% endif %}
 
- <input type="text" id="login-user" data-test-id="login-username" class="input-block-level" placeholder="{{ _('Username')|edq }}" autofocus autocapitalize="none">
+ <input type="text" id="login-user" data-test-id="login-username" class="input-block-level" placeholder="{{ _('Email Address')|edq }}" autofocus autocapitalize="none">
  <input type="password" id="login-password" data-test-id="login-password" class="input-block-level" placeholder="{{ _('Password')|edq }}">
  <span class="pull-right"><small>
  <a href="https://mr-beam.freshdesk.com/support/solutions/articles/43000500137" id="login-forgotpassword" target="_blank" tabindex="-1">