When loading a draft:
If the draft was created from a different account than the current one:
If the draft was in reply to a status, don't allow it to be loaded.
If the draft was not in reply to a status, prompt the user whether
or not to load the draft.
If the draft was in reply to a different status than the current one:
Prompt the user whether or not to load the draft.
Otherwise, load the draft.
Draft replies created from other accounts can't be loaded from different
accounts because the status for inReplyToID of the draft will have a
different instance-local ID if the two accounts are on different
instances.
See #16
The newly created draft needs to be set to the compose VC's currentDraft
so that it gets removed after the status is successfully created.
Also, save the drafts to disk after saving a draft so that crashes don't
cause draft loss.
Shadowfacts