Add check in CrackFrontData for whether crack front node exists, also fix problem with infinite loop for crack front with only two nodes refs #4161
Make DomainIntegralAction create VectorOfPostprocessors for 3D J-integrals closes #4228

Also convert two of the tests over to checking the CSV output generated by this.
Merge pull request #4224 from backmari/crack_front_issues

Check whether crack front node exists in CrackFrontData
Merge pull request #4229 from bwspenc/fracture_integral_vector

Make DomainIntegralAction create VectorOfPostprocessors for 3D J-integrals
Merge commit '057e4e99bcc95d2e752ddcd51b712e0148be374f'