GT-2658 - more finishing touches

docs, exception handling, direct config file parsing instead of system
property.

Ghidra/RuntimeScripts/Common/server/jaas_external_program.example.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# This is a trivial example to show how the Ghidra ExternalProgramLoginModule
+# communicates with the external authenticator.
+#
+# The username and password will be supplied on STDIN separated by a newline.
+# No other data will be sent on STDIN.
+#
+# The external authenticator (this script) needs to exit with 0 (zero) error level
+# if the authentication was successful, or a non-zero error level if not successful.
+# 
+
+echo "Starting example JAAS external auth script" 1>&2
+
+read NAME
+read PASSWORD
+
+
+if [[ ${NAME} =~ "bad" ]]
+then
+	echo "Login failed: username has 'bad' in it: $NAME" 1>&2
+	exit 100
+else
+	echo "Login successful" 1>&2
+fi
+
+