Preserve local drafts on sign out?

[bummytime]

Original issue: https://github.com/wordpress-mobile/WordPress-Android/issues/1989

A user had local drafts in the app, then signed out. The app cleared all of the posts.

Maybe we could:

• Preserve local drafts, even on sign out?
• Show some kind of warning that local drafts will be lost if you sign out.

[maxme]

Note: this was fixed but the implementation was not perfect (the number of cases with wporg/wpcom accoount doesn't help). The best solution to solve this: have local drafts in a specific table and keep that table untouched whatever the user does (signout / signin).