Improve magic startup script

tfw_magic_start.sh

@@ -1,6 +1,8 @@
 #!/usr/bin/env bash
 set -e
 
+[ -z $TAO_PATH ] && echo 'You need to set the "TAO_PATH" envvar to the directory where the TFW repos are cloned!' && exit 1
+
 BACKEND_REPO="${BACKEND_REPO:-tutorial-framework-wip}"
 FRONTEND_REPO="${FRONTEND_REPO:-tutorial-framework-ng}"
 BACKEND_PATH="${TAO_PATH}/${BACKEND_REPO}"
@@ -23,6 +25,7 @@ function run_backend()
     docker run --rm -p $BACKEND_PORT:$BACKEND_PORT -e AVATAO_SECRET=$AVATAO_SECRET $IMAGE_NAME
 }
 
-trap 'kill %1; kill %2' SIGINT
+trap 'exit' INT TERM
+trap 'kill 0' EXIT
 run_frontend & run_backend
-
+wait