Video texture streaming support via external EGLImage textures

Created new StreamVideoNode & StreamVideoMaterial classes
for QSG renderer. These classes duplicate the logic of
chromium's direct renderer GLRenderer::DrawStreamVideoQuad.
Added support for new DrawQuad material in DelegatedFrameNode.
Added support for external textures in MailboxTexture.

Change-Id: If569b07dfef985f9833de7e64eeb3f952026bca4
Reviewed-by: Arvid Nilsson <anilsson@blackberry.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>