Check Steem PR #3286 Unix socket support

**User Story**
https://github.com/steemit/steem/pull/3286, https://github.com/steemit/steem/pull/3205
>This PR adds to steemd the ability to offer a unix-socket webserver (in addition to http and ws).

>For some node operators, they will use nginx or jussi on their front ends, with a steemd node running on the same box. And since TCP over localhost is dumb, I ported in the ability to use unix-sockets.

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

**Additional Context (optional)**
Add any other context about your request here.

## 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 reviewing Steem PR #3286 and PR #3205, the only implementation references named in the issue. No BitShares files, entry points, or tests are identified; done means determining whether the same Unix-socket webserver capability should be supported alongside HTTP and WebSocket services.

Written by the indexing model from the issue text.