Add user wildcard support for perms lookup on login

This is to add support in salt-api for this workaround from https://github.com/saltstack/salt/pull/4547.

/etc/salt/master:
```
external_auth:
  ldap:
    '*': 
      - .*
```
Successful login:
```
HTTP/1.1 200 OK
Content-Length: 248
Vary: Accept-Encoding
X-Auth-Token: 1ea3b72edbb66330ef1e12adcc0ce703f0d27231
Allow: GET, HEAD, POST
Date: Sat, 20 Apr 2013 14:28:17 GMT
Server: CherryPy/3.2.2
Content-Type: application/json
Set-Cookie: session_id=1ea3b72edbb66330ef1e12adcc0ce703f0d27231; expires=Sun, 21 Apr 2013 00:28:17 GMT; Path=/

{"return": [{"perms": [".*"], "start": 1366468097.403254, "token": "1ea3b72edbb66330ef1e12adcc0ce703f0d27231", "expire": 1366511297.403255, "user": "gigantor-kingpin1@ENG.SALESFORCE.COM-salt-bc783bc6-8e88-47ba-bb85-005e63025ab6", "eauth": "ldap"}]}
```