Move FEMap constructor to C file, use default constructors
for std::vectors.
Fix up minor formatting issues.
Adding inverse map 2nd derivative members and accessors.

Allocating space for inverse map second derivatives in initialization
routines.
Adding inverse map second derivative calculations for 3D-in-3D,
2D-in-2D, and 1D-in-1D cases.
Computing inverse map second derivatives for 1D-in-2D and 1D-in-3D
cases.
Augment shape function second derivative calculations with inverse map
second derivatives in 2D and 3D.