Add virtual operations for referral program fee split

**User Story**
As a lifetime member I want to track my referral income.

**Additional Context (optional)**
Strictly this is not a consensus change, however, it impacts numbering in account history, which is relied on by many 3rd-party applications, so it's fair to make it a consensus-upgrade style change, say, only populate the virtual operations after a special time.

**Impacts**
Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.
- [ ] API (the application programming interface)
- [ ] Build (the build process or something prior to compiled code)
- [ ] CLI (the command line wallet)
- [ ] Deployment (the deployment process after building such as Docker, Travis, etc.)
- [ ] DEX (the Decentralized EXchange, market engine, etc.)
- [ ] P2P (the peer-to-peer network for transaction/block propagation)
- [ ] Performance (system or user efficiency, etc.)
- [x] Protocol (the blockchain logic, consensus, validation, etc.)
- [ ] Security (the security of system or user data, etc.)
- [x] UX (the User Experience)
- [ ] Other (please add below)

## CORE TEAM TASK LIST
- [ ] Evaluate / Prioritize Feature Request
- [ ] Refine User Stories / Requirements
- [ ] Define Test Cases
- [ ] Design / Develop Solution
- [ ] Perform QA/Testing
- [ ] Update Documentation

No source file, test, or entry point is named. Start by clarifying the referral fee-split behavior, the account-history numbering impact, and the special activation time; done should include defined protocol and UX requirements plus test cases for the virtual operations.

Written by the indexing model from the issue text.