-Add some enhancements for qmlglsrc
 Some common features for qmlglsrc are added to make app development much easier.

-Add some enhancements for gstplayer
 Some gstplayer API enhancements are added to make it much easier for users to use.
 Without these API enhancements, some features may not be realized
 (like accurate seek, video sink configuration) when using gstplayer API.
 So it would be better if they can be picked.

-Fix a memory leak issue in glupload, which is common