Delete Accounts without locking up app

[rmroot]

connects #1532

Deleting accounts was too slow to be done in a modal that prevented the user to continue to use the application.

• Added ability to delete account and associated data in the "background".
• A toast notification will show in the corner with the progress of the deleting.
• Can queue up multiple accounts to delete.
• Can cancel and pause
• Accounts being deleted cannot be selected and won't show anywhere but account management page