Added Ezviz CAS server functions and mqtt support for push messages.

-Can now enable/disable camera status again. (Binary request to Ezviz CAS server, encrypted with AES and xored serial)
-Added MQTT function for push messages.
(Just create ezviz user with password ezviz on your mqtt broker)
-Refactored code.
*Moved exceptions to seperate file.
*Moved some of the duplicated constants to constants file.
-Updated requirements file.