Review issues found by SonarQube Scanner

See https://sonarcloud.io/dashboard?branch=develop&id=bitshares_bitshares-core for more info.

Most of them are minor issues but are time-consuming to fix, but it's still possible there are critical issues.

This is a meta issue. We can link back found and resolved issues here.

Additional keywords: sonar, scanner.

**Impacts**
Describe which portion(s) of BitShares Core may be impacted by this bug. 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)

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

Start with the SonarCloud dashboard linked in the issue and review the findings on the develop branch. Determine which findings are actionable and link each found or resolved issue back to this meta issue; completion is not defined until the relevant findings have been evaluated and addressed.

Written by the indexing model from the issue text.