Generated platforms declarations for iOS 11

Fixed broken unit-tests
ios layout now run only for the innermost viewcontoller
ios layout for viewcontrollers now implemented with constraints
Added ios11 safeAreas layout support
onMeasure back for frame and tab-view so that they won't throw exception if measure is called on them
Page parents layout updated after page is layout so that inner layout flags are correct

tns-core-modules/ui/layouts/layout.ios.ts

@@ -3,17 +3,6 @@ import { LayoutBase } from "./layout-base";
 
 export * from "./layout-base";
 export class Layout extends LayoutBase implements LayoutDefinition {
-    nativeViewProtected: UIView;
-
-    constructor() {
-        super();
-        this.nativeViewProtected = UIView.new();
-    }
-
-    get ios(): UIView {
-        return this.nativeViewProtected;
-    }
-
     public onMeasure(widthMeasureSpec: number, heightMeasureSpec: number): void {
         // Don't call super because it will measure the native element.
     }