add CDN configuration via admin config service

[davidnuescheler]

it would be great to extend the cache tester to be able to read and write CDN config from / to admin service.

[davidnuescheler]

i think an evolution of https://tools.aem.live/tools/push-invalidation/index.html would be great

[davidnuescheler]

https://labs.aem.live/tools/cdn-setup/index.html