Update login page for 9.3

Update the login page for 9.3 (localhost:8008/nuxeo/login.jsp) to make it respect the new Nuxeo branding guidelines.

• Update logo to use the new Nuxeo logo
• Update colors on the login box to use Nuxeo colors
• Update background image
• Possibly change footer text color so it is readable

Check with Katie for access to background image candidates.

You can use Studio to try things and see how it looks.

login.jsp source code is available at https://github.com/nuxeo/nuxeo/blob/master/nuxeo-services/nuxeo-platform-web-common/src/main/resources/web/nuxeo.war/login.jsp.

Mockup_LoginJSP.png is the goal
(resources attached)