FemRepresentationLocalization initial checkin

- Defines localization with respect to barycentric coordinates
- Adds FemRepresentationCoordinate structure to contain coordinates + FemElementId
- Implementation currently only for Fem3dRepresentation
Add basic constructors to FemRepresentationCoordinate
Add unit tests for FemRepresentationLocalization

Additionally verifies well-formed barycentric coordinates in
FemElement3dTetrahedron::calculateCartesianCoordinate.
Fix cpplint warnings
Move FemRepresentationCoordinate into new h/cpp

- There should be one header file per class.
- In preparation for next commit (renaming FemRepresentationLocalization
to Fem3DRepresentationLocalization).
Rename to Fem3DRepresentationLocalization

Fem3DRepresentationLocalization::doCalculatePosition and
::isValidRepresentation depend on casting a Representation to a concrete
implementation.  The previous FemRepresentationLocalization actually
only worked for Fem3DRepresentation, and the new name reflects that
fact.
Fix cpplint warnings
Rename to FemRepresentationCoordinate::naturalCoordinate

The generalized term for coordinates in fem is "natural coordinate", not
"barycentric coordinate".
Add isValidCoordinate function to fem and femElement

- FemElement::isValidCoordinate checks whether the naturalCoordinate is
properly formed
- FemRepresentation::isValidCoordinate combines FemElement's check with
an additional check for whether the elementId is valid
- Checks whether coordinate is valid in
Fem3DRepresentationLocalization::setLocalPosition
Refactoring in fem tetrahedron and fem localization test

- Use getSubVector, reduce calculations
Initialize variables in FemRepresentationCoordinate constructor
Update documentation in fem localization and fem coordinate
Fix location of "&" in FemElement & FemRepresentation
Cleanup "#include" in fem element, representation, & localization
Add missing doxygen for fem ::isValidCoordinate
Cleanup FemRepresentationCoordinate constructor
Merge branch 'master' into feature/fem-localization
Add stub isValidCoordinate/computeCartesianCoordinate to fem 3d cube

- Previous build failed because these inherited virtual methods were not
implemented.
Fix formatting with "& "
Merge branch 'feature/fem-localization' into 'master'

Add localization for 3d FEM

Merged-on: https://www.assembla.com/code/OpenSurgSim/git/merge_requests/633073