Version 2.0.0

• Reorderable items.
• Refactored Tray into Tray, ItemBox, render_tray() and render_item_box().
• Replaced Item.get_icon_* methods with Item.get_icons() returning IIconLoaders.
• Greying out items.
• Renamed WinIconConfig to WinItemConfig.
• Replaced parameter Tray
• Replaced MenuIcon with MainItem.
• Replaced WinIcon with WindowsItem and WindowItem.
• Add Items to Tray instead of Icons.
• Introduced class Item, rendered as traylib.Icon or gtk.ImageMenuItem.
• Replaced abstract Icon methods with properties.