message: give more details for generating the Documentation under Linux
diff: @@ -49,6 +49,10 @@ Compiling the documentation
  The documentation can be generated using [Doxygen](http://www.stack.nl/~dimitri/doxygen/):
  * Check the BUILD_DOCUMENTATION option when using cmake
  + * cd build
  + * ccmake ..
  + * set BUILD_DOCUMENTATION option to ON
  + * configure and generate
  * cd build/ringmesh/Release
  * make doc-devkit OR make doc-devkit-lite
  