feat: Add command-line compilation

This is performed using the sunshine executable jar, which must be
  separately downloaded, and a bash script in this project, called
  hel2py. Although the process is a bit cumbersome, it
  meets the original goals of this repository, so this will likely
  be the last commit.

hel2py

@@ -0,0 +1,29 @@
+#!/bin/bash
+while [[ $1 = -* ]]
+do
+  case $1 in
+    -h|--help)
+      echo
+      echo "To use this script to 'compile' a helloworld program, you must set"
+      echo "environment variables:"
+      echo "  SUNSHINE_JAR to the full path to the executable sunshine jar downloaded from Metaborg"
+      echo "  ECLIPSE_INSTALL to the directory where your eclipse executable (with Spoofax plugin) resides"
+      echo "  HELLOWORLD_PROJECT to the project directory of this project"
+      echo "(or of course you could make a copy of this script with those directories hardcoded)."
+      echo
+      echo "Usage:"
+      echo "  hel2py [-q] FILE"
+      echo "You can specify -q to suppress standard error output."
+      echo "Writes the Python translation of FILE to standard out."
+      echo "So you can 'execute' the file with"
+      echo "  hel2py -q FILE | python3 -"
+      exit
+      ;;
+    -q)
+      shift
+      exec 2>/dev/null
+      ;;
+  esac
+done
+
+java -jar $SUNSHINE_JAR transform -i $1 -n "Generate Python" -p $HELLOWORLD_PROJECT -l $HELLOWORLD_PROJECT -l "${ECLIPSE_INSTALL}/plugins"