slideshow: update log messages

Change-Id: Ifcf9941707a8770931296750b674fbccc1571f6d
avmediaogl: call gltf_renderer_set_content() only once

Change-Id: Ic4c4b886f5a60508e4f62eb3396850d09ae5d0a0
slideshow\glTF: add a parent window to the OpenGL window

OpenGL window is a SystemChildWindow which doesn't handle
window events as a vcl Window does (call it's event
handler functions and the given event listeners), so
I added a new parent which will handle window events
and capture them from the slideshow's main window.

Change-Id: I06ac87fb85e663e52f2691c1311605b3fd7d3afa
OGLWindow: remove event listeners also when window is disposed

To avoid segmentation fault.
Plus some comments.

Change-Id: I7368b34a29b595f52975f41836d4fe1f63e4e859
OGLWindow: move camera only when one of the key candidates is pressed

Change-Id: I52b3d100512cad569a53d10c9dc819e4548ba928
OGLWindow: use update function for redrawing.

Change-Id: Icca39a44d6a4437f20d120b4032a39f7e74ac066
OGLWindow: First try to rotate camera

For now its too slow to render by mousemove so
use mousebuttonup instead.
It seems gltf_renderer_rotate_camera() method does not rotate
the camera but set the new position of it.

Change-Id: I0fe7895720dbf95acb0963a5ba6dd2a5840d8f6b