HUE-2012 [core] upgrade django auth ldap
HUE-2012 [core] AD multidomain support

ldap_servers takes precidence over normal ldap config.
backward compatible since original ldap config can be provided.
Add server selection logic on front end.
Split tests by configs: test_ldap_deprecated and test_ldap.
The former will test deprecated configs and the later will test new configs.
The Synchronization middleware will choose the first LDAP Server
config when deciding which server to synchronize with.
HUE-2072 [core] Adding support for HTTPS load-balancing

In order to support HTTPS load-balancing that is terminated at the load-balancer level, Hue needs to know that the request came through HTTPS. Django officially supports this by adding SECURE_PROXY_SSL_HEADER to the settings.py file and specifying the HTTP header (X-Forwarded-Protocol) to be set to https.

https://docs.djangoproject.com/en/1.4/ref/settings/#secure-proxy-ssl-header

At the load-balancer level you need to set that HTTP header. Here is the HAProxy example:

```
reqadd X-Forwarded-Protocol:\ https
```
HUE-2072 [core] Updating Proxy SSL support to be optional
HUE-2072 [core] Disable SSL proxy header by default

Add option in desktop/conf.py
Cleanup comments.