Events claimed by a render pass are still propagated further down

[pierremoreau]

This is an issue, for example, when using the SplitScreenPass as moving the divider between the two splits results in the camera moving along.

SplitScreenPass::onMouseEvent() returns true when the divider is grabbed, as expected, but Mogwai's Renderer::onMouseEvent() does not check the return value of the RenderGraph::onMouseEvent() method and so will still call the onMouseEvent() method on the scene (therefore resulting in the camera moving along despite the SplitScreenPass pass claiming the events).

The same issue applies to keyboard events.