prolog-shell: Simple command line Prolog interpreter

Since Prolog isn't the most popular language, define a small
interactive interpreter that users or site administartors can play
around with by downloading the Gerrit WAR file and executing:

  java -jar gerrit.war prolog-shell

Change-Id: I0474b59e6ace24e6e6bfda58f574add3b2bf79e0
4 files changed