Reflect script implementation in olm-utils and dev env setup instructions

Summary: As we decided to store pickling key and pickled olm account instead of keys, olm_config structure and dev env set up needed to be updated.

Test Plan: No need to test those changes.

Reviewers: palys-swm, varun, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: benschac, ashoat, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3211