Add V2 compatible registry authorization.

[aizuddin85]

To resolved #69:

• Add token request for protected registry.
• Do docker login before pulling when registry is part of protected registry.

[aizuddin85]

@sabre1041 changed based on the recommendation. There are still some TODO list that is not critical.

[sabre1041]

@aizuddin85 Works great. As you mentioned, still some TODO's, but those can come in a subsequent PR.

Thanks for you contributions!