Adding custom updater

[IceflowRE]

While trying to add an own updater, i had several problems.

The Job / Updater struct architecture was quite confusing

• it was not documented that the Updater configs Domain and Zone properties are getting overridden.
• i can only configure an updater once, this makes it impossible to use the same updater with two accounts or even with different properties like "project id". Which makes it impossible to update two domains, cause i can only define it once.

Possible solution:

Expose the updater config to the job as well, so it is possible to override all properties.

[we11adam]

Thanks for opening the issue. I'll look into a better design when I have the time, hopefully in a couple of days.