Show only the configured login providers

[anandology]

We are show all Google, FB, MS login buttons even if the client id and secret for them are not added to the config. It should be changed to display the login button of a login provider only if that settings are available in the config.

The settings are:

GOOGLE_CLIENT_ID
GOOGLE_CLIENT_SECRET

FACEBOOK_CLIENT_ID
FACEBOOK_CLIENT_SECRET

MICROSOFT_CLIENT_ID
MICROSOFT_CLIENT_SECRET

[anandology]

Looks like the default configuration provides all these settings and there is no way to delete them. May be we should delete FB and MS from default config.