Setup fails when folder name is invalid - improve logging / diagnostics

> I took your instructions and the Session logs that you added in the CustomActions and compared them to what I get in my own logs.
> The line “Deleting registry value 'OPEN1'” was missing.
>
> After some investigation, I finally found that my issue was due to setting a “ProductManufacturer” ending with a “.”, which induces the creation of a folder ending with a point in Program Files and AppData.
> When doing that, Windows allows the creation of the folder but automatically removes the final ‘.’.
> That is why the CustomAction.CaUnRegisterAddIn did not find the right registry line to delete when checking in the “OPEN” registry in CurrentUser/…/Excel/Options: it was expecting it to end with a ‘.’ whereas Windows silently deleted it.
>
> Maybe adding a verification on the “session[“AddInFolder”]” in the CustomActions.CaRegisterAddIn can prevent anyone else from encountering the same issue (checking that it does not end with a ‘.’ or more generally that it is a valid folder name).