More warnings related to glTF rendering

Use avmedia.opengl to be more explicit.

Change-Id: I07878c3648de2e4786bf8a5144ef0c1fbb5530f1
glTF rendering: first try to move camera position

SystemChildWindow can't handle events by its own
that's why it's parent is used as an event handler.
Mouse pointer specify the active model.
This patch made for editing, in case of slideshow
we have one less window.

Change-Id: If8ac57176b9a0abab518f8d8a06a2a41177a4881