Finite element can now convert point in global coordinates to local coordinates

Finite element can now convert point in global coordinates to local
coordinates.
Finite element is now responsible for calculating its own rotation
matrix.  (Responsibility moved from ElementStiffnessMatrixBuilder)

Started a Math.Net extension project to duplicate Math.Net Matrix and
Vector functionality exactly, but for keyed vectors and matrices.  This
is a work in progress.  This uses a modified Math.Net dll which exposes
class Math.Net.Numerics.Resources  and its methods as public.