[test][2pnc] Separate properties into their own header

test/porousmediumflow/2p2c/chemicalnonequilibrium/main.cc

test/porousmediumflow/2p2c/chemicalnonequilibrium/problem.hh

...orousmediumflow/2p2c/chemicalnonequilibrium/properties.hh

test/porousmediumflow/2p2c/injection/main.cc

test/porousmediumflow/2p2c/injection/problem.hh

test/porousmediumflow/2p2c/injection/properties.hh

test/porousmediumflow/2p2c/mpnccomparison/main.cc

test/porousmediumflow/2p2c/mpnccomparison/problem.hh

test/porousmediumflow/2p2c/mpnccomparison/properties.hh

test/porousmediumflow/2p2c/waterair/main.cc

test/porousmediumflow/2p2c/waterair/problem.hh

test/porousmediumflow/2p2c/waterair/properties.hh

test/porousmediumflow/2pnc/diffusion/main.cc

test/porousmediumflow/2pnc/diffusion/problem.hh

test/porousmediumflow/2pnc/diffusion/properties.hh

test/porousmediumflow/2pnc/fuelcell/main.cc

test/porousmediumflow/2pnc/fuelcell/problem.hh

test/porousmediumflow/2pnc/fuelcell/properties.hh

test/porousmediumflow/2pncmin/isothermal/main.cc

test/porousmediumflow/2pncmin/isothermal/problem.hh