Google Oauth: show progress bar during authentication process

[bugy]

After authenticating with Google OAuth, "Sign in with Google" button stays there for 10-20 seconds without any visible progress indicator. And after that time the page is redirected to index page.

So to avoid confusion it, there should be some indicator and the button should be disabled, probably.

[bugy]

Added a label during authentication process (both for Ldap and Google OAuth)
Also improved google button styling (to better reflect guidelines)