Add explanation comments on the build system files

docker/Dockerfile

@@ -1,3 +1,5 @@
+# Configuration file to setup the Docker container of Redox
+
 FROM rustlang/rust:nightly
 
 ENV IMAGE_NAME=redox-os-docker

docker/docker.sh

@@ -1,3 +1,5 @@
+# This script run the Docker image of Redox
+
 docker run --privileged --cap-add MKNOD --cap-add SYS_ADMIN --device /dev/fuse \
     -e LOCAL_UID="$(id -u)" -e LOCAL_GID="$(id -g)" \
     -v redox-"$(id -u)-$(id -g)"-cargo:/usr/local/cargo \