Use a common configuration for conversion scripts

[dazza-codes]

Fix #6

A new configuration script is added for the LD4P conversion scripts:

• it uses environment variables to define data paths
• it checks conversion script dependencies
  • the java dependency is revised to use one JAR packaged from ld4p-tracer-bullets
  • this revised dependency is checked and used by the MarcToXML conversion
• it wraps the marc2bibframe conversion in a shell function
  • this function is declared in the configuration script
  • it can be modified when a different converter is required
  • it only requires two args, an input and output file path