Cleanup of Visual::Base::SetSize

Removed SetSize/GetSize from Visual::Base
Added SetTransformAndSize() which should be called from either parent
control's OnSizeSet or OnRelayout.
Added method Visual::Base::Impl::Data::GetVisualSize() to calculate event side
size of visual from transform and control size.

Changed SvgVisual::New() to remove incorrect ImageSize. Instead, uses new visual
size.

Updated Internal::Control::OnSizeSet to ensure that the background visual has
a size set to fill the control

Test Harness
------------
Fixed the event thread callback stub to ensure a 30 second timeout instead of
waiting indefinitely.
Updated test cases to ensure that GetClosestImageSize() is set for visuals under
test that require a size in order to pretend to load something; updated test cases
to ensure that ImageView's added to Stage have a size (to pretend to load something)
Updated dummy-control to handle OnRelayout, and to call SetTransformAndSize on all
registered visuals.

Change-Id: I932293adbd117c242704074229c317a51f9a55c0
Signed-off-by: David Steele <david.steele@samsung.com>