By default, exclude feed accounts from list of target folders for Move and Copy #261

When you invoke Quick Folder Move's Move or Copy commands, it lists target folders from all accounts, regardless whether they are mail accounts, news accounts, or feed accounts.

Although Thunderbird does allow messages to be copied or moved to feed account folders, this doesn't make much sense conceptually, and I suspect most users never do so. (An exception would be moving unwanted feed messages to the local Trash folder provided for each feed account, though in this case users would normally use Thunderbird's built-in functionality, such as simply pressing the Delete key.)

I suggest that Quick Folder Move should by default exclude all folders from feed accounts. Probably the best way of handling this on the UI side is to include a "Never match feed folders" checkbox in the Preferences dialog, maybe directly underneath the existing "Never match archive folders" checkbox.

Alternatively (or additionally), the Preferences dialog could allow the user to exclude folders en masse on a per-account basis. This would make it easy for them to select their feed accounts for exclusion. (This is similar to the enhancement requested in #237, except that here we're excluding all subfolders of a given account rather than all subfolders of a given folder.)