Ability to load MEMX instruments from directory file

[Open-Markets-Initiative]

Provide example for loading directory file:

https://info.memxtrading.com/us-options-instrument-directory

The memx dissector will need to be able to work with or without this file.

1. no file: display binary identifier
2. provide tree node with underlying values from MEMX csv

Further options will be added once we have a working prototype.

Use specification actions to add to source generation.