[web] Add constructMeshesFromGeometry description.

web/content/docs/tools/model-preparation/constructMeshesFromGeometry/index.pandoc

++++
+date = "2018-06-19T15:56:57+01:00"
+title = "Construct meshes from bulk mesh and geometries"
+author = "Dmitri Naumov"
+
+[menu]
+  [menu.tools]
+    parent = "model-preparation"
++++
+
+## General
+
+`constructMeshesFromGeometry` is a conversion tool for the `gml` files.  Given a
+"bulk" mesh and the `gml` geometry file the tool generates meshes for all named
+geometries.
+
+The meshes are used for the boundary conditions and provide node ids and element
+ids mappings to the bulk mesh.
+
+## Example
+
+For example a conversion of a mesh from `Tests/Data/LIE/Hydromechanics` single
+fracture 3D project:
+```
+constructMeshesFromGeometry -m single_fracture_3D.vtu -g single_fracture_3D.gml
+
+debug: Reading geometry file '../s/Tests/Data/LIE/HydroMechanics/single_fracture_3D.gml'.
+debug: Project configuration from file '../s/Tests/Data/LIE/HydroMechanics/single_fracture_3D.gml' read.
+debug: The search length for mesh "single_fracture_3D" is 1.000000e-09.
+debug: Creating mesh from geometry single_fracture_3D inlet.
+debug: Found 3 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D outlet.
+debug: Found 3 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D left.
+debug: Found 46 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D right.
+debug: Found 46 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D front.
+debug: Found 1150 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D back.
+debug: Found 1150 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D bottom.
+debug: Found 25 elements in the mesh
+debug: Creating mesh from geometry single_fracture_3D top.
+debug: Found 25 elements in the mesh
+```
+yields new meshes for each named geometry: `single_fracture_3D_inlet.vtu`,
+`single_fracture_3D_right.vtu`, `single_fracture_3D_outlet.vtu`,
+`single_fracture_3D_left.vtu`, `single_fracture_3D_front.vtu`,
+`single_fracture_3D_top.vtu`, `single_fracture_3D_bottom.vtu`, and
+`single_fracture_3D_back.vtu`.
+
+![](single_fracture_3D_geometries.png)
+The figure shows the front part of the mesh with the extracted geometries. Note,
+the lower dimensional inlet boundary, shown as a line.