[test][multidomain] add 1p2c_1p2c test to compare diffusion laws....
[test][multidomain] add 1p2c_1p2c test to compare diffusion laws. MaxwellStefan and Fick's Law produce the same solution for 2 components
[test][multidomain] add 1p2c_1p2c test to compare diffusion laws. MaxwellStefan and Fick's Law produce the same solution for 2 components