RFE: Refactor code to use a config file for tag handling

[bexelbie]

Two goals:

1. make it obvious what translations will occur for various tags and make it easy to change
2. make it easier to add custom preserved tags without having to recompile

This will require that the tag translations in translate.go be refactored out.

[bexelbie]

This will also clean up command line invocations and make sharing configurations easier.