[T/HM] added 3 tests for ideal gases

ProcessLib/HydroMechanics/Tests.cmake

...s/IdealGas/flow_free_expansion/HM_flow_free_expansion.pdf

...ydroMechanics/IdealGas/flow_free_expansion/cube_1x1x1.gml

...ydroMechanics/IdealGas/flow_free_expansion/cube_1x1x1.vtu

...echanics/IdealGas/flow_free_expansion/cube_1x1x1_quad.vtu

...nics/IdealGas/flow_free_expansion/flow_free_expansion.prj

...sion/flow_free_expansion_pcs_0_ts_1000_t_10000.000000.vtu

...roMechanics/IdealGas/flow_no_strain/HM_flow_no_strain.pdf

...HydroMechanics/IdealGas/flow_no_strain/flow_no_strain.prj

...w_no_strain/flow_no_strain_pcs_0_ts_1000_t_100.000000.vtu

...ata/HydroMechanics/IdealGas/flow_no_strain/square_1x1.gml

...echanics/IdealGas/flow_no_strain/square_1x1_quad8_1e2.vtu

...lGas/flow_pressure_boundary/HM_flow_pressure_boundary.pdf

...dealGas/flow_pressure_boundary/flow_pressure_boundary.prj

...ary/flow_pressure_boundary_pcs_0_ts_100_t_4000.000000.vtu

...roMechanics/IdealGas/flow_pressure_boundary/quad_1x10.gml

...roMechanics/IdealGas/flow_pressure_boundary/quad_1x10.vtu