Add Windows 2019 Core

[jimbo8098]

Adds a configuration to build Windows Server 2019 Core. Tested in my own VirtualBox environment, unsure of other environments but the steps used don't differ greatly from the steps used in other environments.

You'll see a reference to headless mode (which I used during debug). I'll raise an issue for that since it could be helpful too.

[jborean93]

From what I can understand the differences between the normal 2019 and 2019 is essentially the WIM label that is used during the install. Currently you should be able to do -e iso_wim_label_2019='Windows Server 2019 SERVERSTANDARDCORE' as an extra variable to the playbook to override the default WIM label that is used. I haven't tested this but this is the reason why I added this var so that people could customise their images as they desired.

For the main set of images, it already takes a lot of time to generate the existing ones for all 3 platforms and I would be very reluctant to add even more to that list.

[jimbo8098]

We could insist on relying on the use of -l during the playbook command to ensure that doesn't happen. Personally, I had no need to create all the boxes within the inventory.yml, I just needed a more up to date server standard and core. I'm happy to admit that it's a tiny change request, perhaps even too trivial to include, but it may help people bring up their required image without needing the check the available WIMs on the media.

Were it there, it would have saved me a few hours since i'd never worked with WIMs before. That said, it was exactly as I assumed on the first day of looking into it.