Calendar: board, day view and undated drafts

The calendar is now easier to work with every day.

• Board and day view. See the week as a board or a single day in detail, and jump between dates with the mini calendar on the side.
• Undated drafts sit in their own strip above the calendar, so you can see at a glance what isn't scheduled yet.
• Profile view per platform shows how the account feed will look, including the empty schedule slots still to fill.
• Social-style post previews everywhere you see a post.
• A Create menu right in the calendar.