Recognize SSO role name for base accounts

[choeflake]

I'm happy with feature #129. In our case we start login via an SSO role (Permission Set). Afterwards we assume an IAM role.

Since #129 the entry role is catched from the AWS Console page. But, the SSO role name which is displayed there has a random string in it. That makes it hard to create a config file with the correct 'role_name' property in it.

The standard role names which is shown in the console is 'AWSReservedSSO_' followed by the user friendly name of the SSO role (Permission Set) and ends with '_'. It would be very helpful if we could extract the user friendly role name.