Added "iOS Design Cheat Sheet"

Hi Bogdan,

I added a new cheatsheet for iOS7 Design screen elements. This is based on ivomynttinen.com/blog/the-ios-7-design-cheat-sheet/ and I have communicated about reusing the data here with Ivo. An attribution has been added to the end and the docset has been tested in my Mac.

Regards
Deepu