Add a conversion utility for Linux/Saxon users

Kevin et. al, this is a start of making it easy for me to use at the command-line.   It might be better if this utility didn't take its defaults (particularly BaseURI) from the script, but instead/also read a file $HOME/.marc2bibframe 

More importantly, I want to explore the notion of where to put utilities like this, e.g. top-level, a separate bin directory, etc.