Correct mobile redirect (open in app) to allow opening the right document

• install nuxeo mobile and get authenticated
• get a doc link
• open in safari without being authenticated
• click on "open in app" in the login page

• Expected result : mobile app is opened, the document view is displayed
• Actual result : mobile app home page is displayed

Note : broken since :
https://github.com/nuxeo/nuxeo/commit/b53762ebc2e6570d5d33acd96597297b02513212#diff-48e11c544527ef0796225a06c36a6b6bL540

Notes :
"Should we get it back, or should we read the `document.cookinsnuxeo.start.url.fragment` to compute the right URL to open the mobile app?"
"We'll need to retrieve it from the cookie as some browsers drop the fragment through the redirect"