[T/LiquidFlow] Specify processes explicitly as linear

Tests/Data/Parabolic/LiquidFlow/InclinedMeshElements/FractureIn3D/fractures_in_3D.prj

@@ -20,6 +20,7 @@
             <aperture_size>
                 <parameter>fracture_thickness</parameter>
             </aperture_size>
+            <linear>true</linear>
         </process>
     </processes>
     <media>

Tests/Data/Parabolic/LiquidFlow/SimpleSynthetics/PrimaryVariableConstraintDirichletBC/cuboid_1x1x1_hex_1000_Dirichlet_Dirichlet_1.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>-0. 0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/SimpleSynthetics/PrimaryVariableConstraintDirichletBC/cuboid_1x1x1_hex_1000_Dirichlet_Dirichlet_2.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>-0. 0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/SimpleSynthetics/PrimaryVariableConstraintDirichletBC/cuboid_1x1x1_hex_1000_Dirichlet_Dirichlet_3.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>-0. 0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/Unconfined_Aquifer/BC_BC/TestSet_01.prj

@@ -17,6 +17,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/Unconfined_Aquifer/BC_BC_RECHARGE/TestSet_01.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/Unconfined_Aquifer/BC_BC_RECHARGE2/TestSet_01.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>

Tests/Data/Parabolic/LiquidFlow/Unconfined_Aquifer/BC_BC_STORAGE/TestSet_01.prj

@@ -18,6 +18,7 @@
                 <secondary_variable internal_name="darcy_velocity" output_name="v"/>
             </secondary_variables>
             <specific_body_force>0.0 0.0</specific_body_force>
+            <linear>true</linear>
         </process>
     </processes>
     <time_loop>