Add the KADEPLOY_VERSION env variable

doc/Kadeploy.tex

@@ -2311,6 +2311,7 @@ On an \emph{Other} environment, you eventually have to update your bootloader in
 \subsection{Kadeploy3 Environment variables}\label{sec:env_vars}
 When writing a script for an admin pre-install, an admin/user post-install or some custom operations, you can use the following environment variables :
 \begin{itemize}
+\item \texttt{KADEPLOY\_VERSION} : the version of the Kadeploy3 server running
 \item \texttt{KADEPLOY\_CLUSTER} : cluster on which the pre/post install is launched
 \item \texttt{KADEPLOY\_ENV} : environment deployed
 \item \texttt{KADEPLOY\_ENV\_KERNEL} : the path to the kernel file inside the deployed environment directory