Visual Challenge - Expedia Flights

[alexeystrakh]

This PR implements the layout of the Flight Booking experience of the Expedia application. The original page looks like below. I've also created a quick prototype in Figma in order to add some elements:

The Xamarin.Forms Visual Implementation

iOS	Android

What Went Well

• Easy adoption of new controls (old controls with a new look)
• The previewer works so I skipped a few dev cycles
• Good docs with the list of currently implemented controls and also some samples
• Detailed blog post by David on how it works, and what to expect

What didn't

• Previewer doesn't show material look
• Picker background wasn't changeable on Android (iOS works fine), you can see it in my demo

Would like to have

• More controls adopted (like the Switch control and the rest)
• More control over paddings, margins and other elements of material implementation (e.g. Entry Placeholder color when text is empty and a different color when it's pushed above the text)