Fix typo in FemElement3DTetrahedron ("stiffness" instead of "mass")
Add range check on FemElement3DTet nodeId in ctor
Missing 'override' keyword for FemElement3DTet::addMatVec
Add FemElement3DCube + UnitTest + upgrade ExampleFem3D

This Fem element uses a Gauss-Legendre quadrature to numerically evaluate integral terms with a discrete sum.
This math tool has been added to the Math library, but do not have any UnitTest because it is only a set of paired data <parametric coordinate, weight>.
Merge branch 'master' of git.assembla.com:OpenSurgSim into feature/femElement3dCube

Conflicts:
	Examples/Fem3D/ExampleFem3D.cpp
FemElement3DCube: rename some single letter variables + more doc + fix a bug

neta -> eta (that was a typo)
m_coefX -> m_shapeFucntionsXSign as these are really containing a sign (+1 or -1) and are related to shape functions
m_M -> m_mass
m_K -> m_stiffness
evaluateB ->evaluateStrainDisplacement (note that I kept the variable as B for simplicity in the equation)
evaluateJ kept as is but more details are given in the doc now. This one is hard to name differently...

Change doc style for the Shape function N because of the Latex newline \\ causing warnings under Linux.

Also fix a bug in the stress/strain evaluation. They were not integrated properly using the Gauss-quadrature rule.
FemCube: coding standard + improve doc + use index and nodeId when appropriate
Fem cube: precise the node ordering rule and write UnitTest to demonstrate it.

The unit test goes over all the cases (correct and incorrect).
For each incorrect one, an ASSERT is triggered, printing a message on the console.
So, that is a lof of print for 1 unit test.
Math: Gauss-Legendre doxygen doc more Latex-ish
ExampleFem3D clean the example (more space between obj + remove 4th column)
ExampleFem3D remove global variables by creating a Cube class.
Change passed parameter for runtime to weak_ptr and add cecks
Refactor inititialisation sequence

Add Runtime as a constructor parameter in the Scene
Call initialize from scene::addSceneElement and SceneElement::addComponent
Remove initialize calls from Runtime
Remove wakeUp from SceneElement
Make runtime have a default scene and remove setScene from Runtime
Fix up examples to the new scene and scenelement interface

This got a little bit out of hand, the steps could have been done smaller increments ... sorry
Documentation and formatting updates
Fix ViewElementTest, SceneryRepresentationTest

Remove wakeUp from ViewElementTest
Change SceneryRepresenatationTest to follow new initialization sequence
Add empty filename check for SceneryRepresentation
Cleanup, clarifications to the documentation and error messages

Fixed slight logic error in Scene::addSceneElement call
Documentation updates
FemElement3DCube: improve doc + explicit nullptr comparison + clean up
Clean up + rename N->shapeFunction + dedicated struct gaussQuadraturePoint…
Merge branch 'master' of git.assembla.com:OpenSurgSim into feature/femElement3dCube