Added Smilei download phase + README

Smilei/README.md

+Description:
+============
+
+Presentation
+------------
+
+Smilei is a Particle-In-Cell code for plasma simulation. Open-source, collaborative, user-friendly and designed for high performances on super-computers, it is applied to a wide range of physics studies: from relativistic laser-plasma interaction to astrophysics.
+
+Technical information:
+----------------------
+
+* website : https://smileipic.github.io/Smilei/index.html
+* Scientific domain : laser-plasma
+* Language : C/C++
+* Parallelism : MPI + OpenMP
+* GPU acceleration : No  
+* Scalability : high
+* Vectorization: high
+
+
+Compilation and simulation:
+===========================
+
+Download:
+---------
+
+Sources are available at: https://github.com/SmileiPIC/Smilei
+
+For the test, we will use a specific release. To download this release, run:
+
+```
+./download.sh
+```
+
+Compile:
+--------
+
+Information (if needed) about how to compile the application. 
+
+For instance:
+
+Compile the code using:
+```
+source machines/occigen-bdw/env
+./compile.sh
+```
+
+`machines/occigen-bdw/env` contains the information for compilation (module load gcc openmpi lapack hdf5 ...)
+
+Run and validate the simulation:
+--------------------------------
+
+For each test case, given in a separate folder (e.g. testcase_small), you can find three scripts:
+
+*  prepare.sh: prepare the simulation (move data to the right location, recompile some minor changes, ...)
+*  run.sh : run the application and print out the evaluated metric
+*  validate.sh: validation of the simulation on a scientific point of view
+
+For running and validating the simulation, one should be able to do:
+```
+cd testcase_XXX
+./prepare.sh
+./run.sh
+./validate.sh
+```
+And getting no error code returned.
+Those steps can also be used in a batch file for running the simulation using a job scheduler.
+
+
+
+

Smilei/download.sh

+git clone https://github.com/SmileiPIC/Smilei.git
+cd Smilei
+git checkout v4.3
+cd -

Smilei/testcase_small/README.md

+Test case presentation
+======================
+
+The small test case is a very well balanced plasma simulation. This test case is very well vectorized and can be tuned to scale up to a thousand of node if necessary. 
+
+
+Case profile
+------------
+