Roles and Permissions for Gramex SAAS

[shraddheya]

ADD Roles and permissions model to be used in SAAS.

Adds a new database in storelocations by the name of roles.db with tables

• roles: roles and users mapping
• permissions: permissions and roles mapping
• user_permissions: mapping for extra permissions that can be assigned to some user

This module adds two new fields in attrdict of handler.current_user and session['user'] name:

• roles
• permissions

[sanand0]

Looks mostly good, @shraddheya. Let's discuss and test it out over a call? Thanks!