Updated 'Appearance' sample

[mykyta-bondarenko]

The sample crashes on launch. Loags are available here.

• the project was re-created
• root folder was renamed from IntroToAppearance to Appearance
• using storyboard
• updated ReadMe's link

[conceptdev]

Redirect for the old sample name in place https://github.com/xamarin/documentation/commit/776fa81049cd3d662bc22912552f2c64d1e01a98