Ubuntu 20.04 LTS support

[abitmore]

User Story

Ubuntu 20.04 LTS (Focal Fossa) has been released 2 months before. As a user I'd like it gets supported by BitShares.

• Perl issue Fix for perl issue building cli_wallet on Ubuntu 20 with PERL5LIB in environment #2236
  - [ ] cli_wallet TLS hand shake issue cli_wallet -s wss://{ANY VALID AUTHORITY}/ws fails with 'TLS handshake failed' #314 (comment) (note: can not reproduce the issue)
• increase fc::fwd<impl size in include/fc/network/tcp_socket.hpp for newer boost lib (Increase size of tcp_server. bitshares-fc#224 or add sizeof checks to impl declaration in tcp_socket.hpp for compatibility bitshares-fc#234 and Ubuntu 20.04 support #2347)
  • the size was different on Windows, better check too (add sizeof checks to impl declaration in tcp_socket.hpp for compatibility bitshares-fc#234 and Ubuntu 20.04 support #2347).
• update docs including README (Update README for Ubuntu 20.04 support and etc #2349), Wiki (main page, build pages)(Update info for 5.2.0 release #2429), dev.bitshares.works (Update supported boost version range dev.bitshares.works#199) and etc
  • note: README in develop branch can be updated when the code is ready. Other docs need to be updated when doing a new release, but not before it.

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)

CORE TEAM TASK LIST

• Evaluate / Prioritize Feature Request
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
• Perform QA/Testing
• Update Documentation

[philmb3487]

I might be willing to do look into the rest of these tasks. I have 2 open PR's for them as now.

[abitmore]

Latest FC is compatible with Ubuntu 20.04 (see bitshares/bitshares-fc#236).

[abitmore]

Done.