Add thermal deformation example

[streeve]

Adds temperature dependent stretch with new example and general way to include thermal physics

Initially only implemented for PMB and without fracture

• Temperature communication
• Thermal strain energy

Blocked by #89

[pabloseleson]

@streeve : Put examples inside folders:
mechanics
thermo-mechanics

[streeve]

@pabloseleson I've fixed the communication issue I was seeing and rearranged the examples as you suggested. Please give a final review after checking that it runs ok on your end

[pabloseleson]

There is an issue when temp0 is not 0.

[pabloseleson]

I tried adding the following to thermal_deformation.cpp. Files were created but with no content:

// ====================================================
//                      Outputs
// ====================================================
// Output displacement along the x-axis
createDisplacementProfile( MPI_COMM_WORLD, num_cells[0], 0,
                           "xdisplacement_profile.txt", *particles );

// Output displacement along the y-axis
createDisplacementProfile( MPI_COMM_WORLD, num_cells[0], 1,
                           "ydisplacement_profile.txt", *particles );

[streeve]

@pabloseleson ready for final review