Add extension pack support for dictionaries

[salsferrazza]

Figure out issues with Sebastian Tomac's converter from 2011 or apply extension pack zipfiles via CLI or filesystem convention. This would obviate XML merging of manually patched QuickFIX dictionaries. Or fix2json can stop using qfx dictionaries and just use native repository definitions and extension packs, although will have to make sure FIX licensing is compatible with distribution of those assets alongside fix2json.