[Delivers #43555163] CDN Streaming Container functionality

**Story:***
https://www.pivotaltracker.com/story/show/43555163

Method ```GetContainerCDNHeader()``` already existed but was returning ``` Dictionary<string,string>``` changed it to return ```ContainerCDN```.

Added ***x-cdn-ios-uri*** to ```ContainerCDN```, updated integration tests.

Removed private method ```IsContainerCdnEnabled()``` since we don't have to parse header value to find out if a container is CDN Enabled, now we can do ```ContainerCDN().CDNEnabled```