Clean up FC

**User Story**
As a developer I want to have the FC library cleaned up in order to get rid of broken/obsolete/unused code and reduce maintenance effort.

Much of the code in FC predates C++-11 and modern Boost. Both C++-11 and Boost have standardized or at least well-proven replacements for much of FC. We should get rid of all code in FC that is either unused by the core, or for which standard and/or Boost replacements exist.

**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)
- [x] Performance (system or user efficiency, etc.)
- [ ] Protocol (the blockchain logic, consensus, validation, etc.)
- [x] Security (the security of system or user data, etc.)
- [ ] UX (the User Experience)
- [x] Other (please add below)
Code quality

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

Start by auditing the FC library and identifying how BitShares Core uses it. Compare the remaining code with C++11 and modern Boost replacements, then determine which parts are unused, obsolete, or duplicated. Done means the unnecessary FC code is removed or replaced without affecting the core, with performance and security impacts checked.

Written by the indexing model from the issue text.