Rework Dropdown component

[gorbit99]

This PR reimplements the dropdown component from the ground up. The new version should be mostly compatible with the old behaviour with the following differences:

• The component now animates the opening and closing of the dropdown
• It can now be navigated with the keyboard, which wasn't possible before
• The text on the dropdown is now left aligned, instead of center aligned (brought over from flightlist)
• Removed the fontName parameter of the dropdown, instead implementing the feature in the single place it was used
• Removed the "component" property from the dropdown items and merged it with "label"

[loucass003]

Z-offset issues

Clipped by overflow-hidden (Was the main reason of the portal)