Refactor user authorization models

Currently the refactored db relations are as follows:

user <-> permission <-> role <-> role_operation <-> operation
                                                       |
                                           action on resource type

in this way, user can have the permission to perform a action on a
resource type, and currently not considering specific resource
authorization

Signed-off-by: walteryang <walteryang47@gmail.com>
Add initial db content related to user model

1. added a user named 'admin@internal.com' as initial admin user
2. added some default operations and roles

run rake db:setup to populate the db with these values

Signed-off-by: walteryang <walteryang47@gmail.com>