Some miscellaneous cleanup while review the diff vs master

Fixed a blind cast to VideoItem in HTTPGetHandler
Restored HTTPRequest.uri to "protected" access
Fixed a couple copyrights/author tags.
Merge branch 'cablelabs/master' of github.com:cablelabs/rygel into cablelabs/master
Renamed/split PlaySpeed-related classes

Per feedback on gnome bugzilla 710628, split DLNAPlaySpeed.vala (which had
 3 classes) into three separate files and removed some methods on PlaySpeed
 class (is_trick_rate() and is_negative()) since is_normal_rate() and
 is_positive() can be used to accomplish the same.

Took "DLNA" off DLNAPlaySpeedRequest and DLNAPlaySpeedResponse.

Did a couple tests with TimeSeekRange, PlaySpeed, and both in the same request.