Update for AppleTV modules

Hi,

This pull request contains code changes for the following modules:

* **appletv_display_video** - Description update. Proper use of default options. Deregistered/unused advanced datastore options because it uses Rex and not HttpClient to make HTTP requests. Supports username/password, SSL, proxies, validates URL datastore option. Sends the HTTP request as a new thread, that way you're not stuck in the module staring msfconsole. There is a ```stop_play``` that I haven't quite figured out how to implement, so I left the method there for future work.

* **appletv_display_image** - Description update. Proper use of default options. Deregistered/unused advanced datastore options due to the same reason. Supports username/password, SSL, proxies. Sends the request as a new thread.

* **apple_tv_login** - Builds a custom credential array by overriding/modifying some of the credential-building methods from AuthBrute. Description update. Deregistered some of the unused options. Note that STOP_ON_SUCCESS is set to true by default, because since the device only allows one password, there is no point to try more after one is found.

All new changes have been tested on our AppleTV device.