CLDLink manual creation

[lm2s]

Direct/manual creation of CLDLink should be possible, to perform fetch of shortURL. The only info needed for the shortURL fetch operation is sessionIdentifier and shareId, which can easily be supplied.

Example with initializer (could also be done by making these properties readwrite):

let link = CLDLink(shareId, CLDSession.defaultSession().sessionIdentifier)
link.fetchShortURLWithResultBlock({ (url) -> Void in ...

This functionality is important when trying to fetch a shortURL long after an item public link has been fetched, instead of performing another public link fetch to then fetch the shortURL, it could be done directly and instantly.