0.3.1

Added — top bar knobs (CalendarMetrics; defaults keep the stock look)

• dateRowAlignment: .edges — the departure at the leading edge, the return at the trailing edge,
  the arrow between them (default .centered), with dateRowHorizontalPadding.
• topBarBackIconSize, topBarCloseIconSize — the chevron's and the cross's glyph sizes.
• returnClearIconFilled: false — an outlined circled cross on the return label.