added Open Standard for a HIVE Account Referral System support

Added support for the Open Standard for a HIVE Account Referral System on condenser with this merge request.

Link: https://hive.blog/hive/@hiveonboard/open-standard-for-a-hive-account-referral-system

Post about these changes: https://hive.blog/hive/@roomservice/merge-request-referral-system-support-for-condenser-hive-blog

What it does:

• Reads the beneficiaries array from signed in account (field json_metadata) and place it into the redux store
  • Reference User: https://hiveblocks.com/@referral-tester
• Defaults beneficiaries for new posts for signed in account
  • Reference Post: https://hive.blog/testing/@referral-tester/test-post-for-open-standard-for-a-hive-account-referral-system
• Signed in account can always Opt-Out from the Referral System going to Settings -> Preferences -> Referral System DropDown
  • Setting will be persisted in the redux store
• Default beneficiaries will be removed for new posts for signed in account if Opt-Out
  • Reference Post: https://hive.blog/testing/@referral-tester/45keom-test-post-for-open-standard-for-a-hive-account-referral-system

It would be a great success for evolving the Referral System if this request will be accepted.