1) Added roles check for all the rails admin Menu.

TODO: Need to restrict the list shown based on the user's accessible centers.

2) Done Registration flow.

Currently it uses gmail for SMTP, we need to change that to a proper SMTP server.

Flow :

1) User can login with Google Acccount. We need to check if it works with Isha's email id
2) If user is not present in our system, he will be redirected to fill up a registration form which will be pre-populated with the values from Google.
3) User has to fill up the approver's email to get role and access to centers.
4) Approval mail is triggered to the approver.
5) Approver can login to the system and he can add access privilleges.