Rename variable
closes #3678
Add CrackFrontData PostProcessor ref #3671

This postprocessor currently calculates the value of a user-specified variable at
a specified node index along the crack front used for J-Integral calculations.

I'll expand it to output other data about the crack front as well.

Next step is to add an option to JIntegralAction to create one of these for
each point along the crack.
Merge pull request #3679 from permcody/rename_variable

Rename variable
Rename JIntegralAction to DomainIntegralAction, make general ref #3680

The JIntegral block in the input file is replaced with DomainIntegral,
and an additional parameter "integrals" must be specified, which contains
a list of integrals that are to be computed.  This paves the way for adding
the interaction integrals, and having the option to compute multiple types
of domain integrals in one run.
Merge pull request #3672 from bwspenc/crackfrontvariable

Add CrackFrontData PostProcessor
Merge pull request #3682 from bwspenc/rename_jintegral

Rename JIntegralAction to DomainIntegralAction, make general
Dummy #000
Lode angle in RankTwoTensor now accepts argument to deal with
precision loss problems

Mohr Coulomb added - 12 tests added ranging from trivial exception
tests, to somewhat more complicated tests that map out the yield
surface with hardening and smoothing.

I'd really like people to start using this so we make the algorithms
more robust.  I don't think there are any explicit bugs, but this
particular non-linear root-finding problem is numerically more
challenging than the other plasticity models, so for particular
combinations of tolerances, etc, the algorithm could fail to converge.
It would be nice to know what those combinations are so we can build
a better algorithm!