Added DisplacementAboutAxis BC and tests refs #4276
Adding LinearCombinationAux

LinearCombinationAux is a kernel that computes a linear combination of
two vectors of variables, i.e. u = \Sum a_i * b_i

Closes #4281
Merge pull request #4286 from andrsd/lin-comb-aux

Adding LinearCombinationAux
Merge pull request #4277 from backmari/rotational_displacement

Added DisplacementAboutAxis BC and tests
Merge pull request #4289 from dschwen/tensorpre_4183

Cleanup on Tensor classes
Add named constructors, mixed product (#4183)