Log initialization failure of SceneElement in Scene::addSceneElement()
Not loading mesh if no file name is given in RigidRepresentationBase
Fix PhysicsRenderTest
Remove logging in Scene when initialization of SceneElement failed.

Logging should be done at the site of failure instead of the upper level
which receives the failure.
Merge branch 'master' into fix/PhysicsRenderTest

Conflicts:
	SurgSim/Physics/RenderTests/RenderTestRigidBodies.cpp
Merge branch 'fix/PhysicsRenderTest' into 'master'

PhysicsRenderTest fix

Merged-on: https://www.assembla.com/code/OpenSurgSim/git/merge_requests/942953