Add ElasticEnergyMaterial shell (#4269)
Make phase_field depend on tensor_mechanics (#4269)
Implement derivatives in ElasticEnergyMaterial (#4269)
Add test for ElasticEnergyMaterial (#4269)
Register ElasticEnergyMaterial and fix test (#4269)
Declare variables in the loop body, add missing gold file (#4269)
Merge pull request #4376 from dschwen/elasticenergy_4269

Add elastic free energy material