Fix drafts being allowed outside of Drafts/Trash and non-drafts being allowed inside Drafts

[paw-hub]

Ensure people do not move drafts outside of either the drafts folder or trash folder. Also ensure people do not move non-drafts into the drafts folder.

To do this, we do the following:

• If the selection is not a draft, prevent 'Drafts' from being listed in all move button dropdowns.
• If the selection is a draft, prevent anything that is not 'Drafts' or 'Trash' from being listed in all move button dropdowns.
• Do not allow mails to be dragged into disallowed folders.
• Prevent drafts and non-drafts from being moved simultaneously.
• Prevent inbox rules from targeting the drafts folder.

Fixes #3241