Win-acme: Avoid using registry

[Trapulo]

I noticed that renewals planning is saved in registry. I suggest to move it to a local file, in same folder as the exe (an xml file, or a json as the current data in registry).
This will make the application more portable, and will remove an hard link to the specific Windows user running it. So, for example, I can schedule renewals with a service account, also system. And I will not lost data if I change (delete) user.

[rkerber]

This could be part of #146.

[Trapulo]

Yes, I think it can be a subtask of #146

[rkerber]

If anyone wants to see this enhancement, add your +1 (via add your reaction) to the first comment of issue #146.