Inbox items should stay in inbox until moved to another list

Originally part of Inbox ideas.

Inbox items with a plan should stay visible inside inbox. They wouldn't show in today. The exception would be if they had a plan date of today. Inbox items should only move out of inbox if they are moved to another list.

Reasoning: Quick way to reference back to tasks as you organize them. Users don't expect that the task will disappear right away after adding a plan date.