Mesh from jpg image file

In this commit the image files are simply read into memory and a 2D
four node quad mesh is constructed (along with the sphere mesh).

The user can also select the mesh size in pixels.
DIC Physics

Reads in a jpeg file of the reference state,
constructs a mesh from the image dimensions,
and computes a cross correlation with another image file of the
deformed state.

Has also been linked up with other physics like peridynamics
so they can use the computed displacements as a boundary condition.

Images must be 8bit grayscale.