update of the installation description for OTB

docs/source/installation.rst

@@ -30,8 +30,11 @@ Orfeo Toolbox (OTB) and its python bindings
 As indicated in the `OTB installation 
 <https://www.orfeo-toolbox.org/CookBook/Installation.html#linux-x86-64>`_, you need to modify some files to have functional OTB installation :
 * To use Python3 you need in the file otbenv.profile modify ``lib/python`` into ``lib/python3``, for variable PYTHONPATH
+
 * You need to add a symlink to libpython3.5m.so.rh-python35-1.0 to make it works. The method is described in the FAQ on the OTB installation page. Note that you can create this symlink regardless of your version of Python3 by pointing to the file libpython3.Xm.so..
+
 * Finally, you must initialize the environment each time you launch a terminal
+
 .. code-block:: console
 
     source otbenv.profile