Add stress output in a direction

Ref #2929
Merge pull request #2932 from jasondhales/stress_2929

Add stress output in a direction
Removing unnecessary LinearElasticityModule file.

Refs #2937.
Fixing unused variable warnings.

Refs #1777.
Merge pull request #2938 from jwpeterson/linear_elasticity_module

Removing unnecessary LinearElasticityModule file.
Merge pull request #2939 from jwpeterson/fixing_warnings

Fixing unused variable warnings.