[Geary] Feedback on closing draft messages

[Adam Oxford <adam areaofeffect tv>]

Thanks for responding to issue #807 regarding draft messages which are discarded rather than saved on closure. 

As a bit of user feedback I'd like to offer that this can create problems when composing mails that aren't immediately sent.

For example, if you click off a Geary window while composing a mail (or go make a cup of coffee), then tap a new mail desktop notification it will delete the draft and the undo button is small and only appears briefly. There are many other scenarios where a mail is left uncompleted, in my experience particularly if Geary is used to manage multiple accounts.

Previously Geary had a warning popup that prevented accidental deletion, which worked.

Clearly user laziness in not opening new mails in a separate composing window or manually saving, but relying on autosave is a hard habit to get out of.