Added info about git submodule

Signed-off-by: Jim Martens <github@2martens.de>

body.tex

@@ -629,7 +629,8 @@ sub directory.
 
 Lastly, the SSD implementation from a third party repository
 has been modified to work inside a Python package architecture and
-with eager mode.
+with eager mode. It is stored as a Git submodule inside the package
+repository.
 
 \section{Preparation of data sets}