Add a script that helps installing a DS's Python3 deps into the itango container

tools/itango/install_requirements-DS.sh

+# Find the path to the device server's requirements.txt file
+# on the Docker's host but relative to the /hosthome directory
+# in Docker the user's # mounted ${HOME}).
+# ATTENTION
+# This is assuming that the device server's requirements.txt file
+# exists # on the Docker's host in the user's ${HOME} directory.
+runThis=$(basename ${0})
+runThis=${runThis}/requirements.txt
+if [ -f ${runThis} ]; then
+    myDir=${PWD}
+else
+    myDir=${PWD}/$(dirname ${0})
+fi
+deviceServerPath=${myDir//${HOME}\//\/hosthome\/}
+
+docker exec -it itango python3 -m pip install -r ${deviceServerPath}/requirements.txt