[doc] fixed old documentation

Author: chleh

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/CentralDifferences/c_CentralDifferences.md

@@ -0,0 +1 @@
+Assembles the Jacobian using central differences.

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/CentralDifferences/t_component_magnitudes.md

@@ -0,0 +1,5 @@
+Representative magnitudes for the components of the solution vector of the
+process being assembled.
+
+E.g., for the HT process there are two components: pressure and temperature,
+thus two values are expected in this case.

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/CentralDifferences/t_relative_epsilons.md

@@ -0,0 +1,5 @@
+Specifies the magnitudes of the perturbations used to compute the numerical
+Jacobian.
+
+The magnitudes are specified relative to the \c component_magnitudes.
+The number of values given must match the one of the \c component_magnitudes.

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/i_jacobian_assembler.md

@@ -1 +1,2 @@
-\ogs_missing_documentation
+This setting makes it easy to switch between different ways to assemble the
+Jacobian, e.g., analytically or numerically using finite differences.

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/t_component_magnitudes.md

@@ -1 +1 @@
-\ogs_missing_documentation
+The type of the Jacobian assembler to be used.

Documentation/ProjectFile/prj/processes/process/jacobian_assembler/t_relative_epsilons.md

@@ -134,10 +134,10 @@ createCentralDifferencesJacobianAssembler(BaseLib::ConfigTree const& config)
     config.checkConfigParameter("type", "CentralDifferences");
 
     // TODO make non-optional.
-    //! \ogs_file_param{prj__processes__process__jacobian_assembler__relative_epsilons}
+    //! \ogs_file_param{prj__processes__process__jacobian_assembler__CentralDifferences__relative_epsilons}
     auto rel_eps = config.getConfigParameterOptional<std::vector<double>>(
         "relative_epsilons");
-    //! \ogs_file_param{prj__processes__process__jacobian_assembler__component_magnitudes}
+    //! \ogs_file_param{prj__processes__process__jacobian_assembler__CentralDifferences__component_magnitudes}
     auto comp_mag = config.getConfigParameterOptional<std::vector<double>>(
         "component_magnitudes");