Adding the ability to configure the logo from the administration

Hi everyone,

I’m interested in progressing on the implementation of XWIKI-16039 which is about providing the ability to change the logo from the administration. In order to progress on this, we need to agree on the target pages and XClass that will be used. I’ve added an Implementation proposal section to the corresponding design page. That’d be great to know if you’re fine with the proposal so that I can proceed with a pull request along this line.

Cheers and thanks