[T] Example of the <include>-syntax.

Tests/Data/Elliptic/cube_1x1x1_SteadyStateDiffusion/SteadyStateDiffusion.xml

+<process>
+    <name>SteadyStateDiffusion</name>
+    <type>STEADY_STATE_DIFFUSION</type>
+    <integration_order>2</integration_order>
+    <process_variables>
+        <process_variable>pressure</process_variable>
+    </process_variables>
+    <secondary_variables>
+        <secondary_variable internal_name="darcy_velocity" output_name="v"/>
+    </secondary_variables>
+</process>

Tests/Data/Elliptic/cube_1x1x1_SteadyStateDiffusion/cube_1e1.prj

@@ -3,17 +3,7 @@
     <mesh>cube_1x1x1_hex_1e1.vtu</mesh>
     <geometry>cube_1x1x1.gml</geometry>
     <processes>
-        <process>
-            <name>SteadyStateDiffusion</name>
-            <type>STEADY_STATE_DIFFUSION</type>
-            <integration_order>2</integration_order>
-            <process_variables>
-                <process_variable>pressure</process_variable>
-            </process_variables>
-            <secondary_variables>
-                <secondary_variable internal_name="darcy_velocity" output_name="v"/>
-            </secondary_variables>
-        </process>
+        <include file="SteadyStateDiffusion.xml" />
     </processes>
     <media>
         <medium id="0">