Remove unnecessary references to manifest
Created by: nicosang
The main idea behind this Pull Request is to centralize the access to manifestModel object. When a manifest is downloaded, the callback 'onManifestUpdated' is called. I suggest to update Periods array in DashAdapter class. The manifest is added to each period object. So, we don't need, in each file, to set manifest as parameter. There is an exception : it's for getTracksForTypeFromManifest and getStreamsFromManifest functions of MediaPlayer. Those functions could be called for an unplayed stream.