eigen kernels may not cover all eigen variables, so provide a function to mark a eigen variable #2888
fix a bug in the scaling which requres regolding #2888
make AddVariableAction able to add an eigen variable and create a test with deficient B #2888
Merge pull request #2889 from YaqiWang/eigen_var_2888

Eigen variable add 2888
Merge commit '52a75b7e46ab9f82101aa9e237543dc380d00ed7'