Add a sha256 hash over the OCA Bundles file to the generated JSON lists of bundles

[swcurran]

This addresses #82 by adding a sha256 hash over the OCA Bundle to the JSON lists of bundles. A client can load the list and check the hash against a saved value to determine if the OCA Bundles needs to be reloaded.

@wadeking98 -- still a bit nervous this will break production. Could you run a local test of the current released BC Wallet code using my branch (https://github.com/swcurran/aries-oca-bundles/tree/add-sha256-hash) that I'm trying to merge to make sure that the updated JSON file with the sha256 field added doesn't break anything in the released BC Wallet people are using?

If you are confident -- feel free to approve :-)

[wadeking98]

testing and working with local copy (tested LSBC test credential and IDIM prod person credential)