Add new --proxy-cache option

[shuizhongyueming]

Add a new option --proxy-cache to cache response from the proxy server and will auto decompress the response if it is compressed based on the content-encoding header

Contributor checklist

• Provide tests for the changes (unless documentation-only)
• Documented any new features, CLI switches, etc. (if applicable)
  • Server --help output
  • README.md
  • doc/http-server.1 (use the same format as other entries)
• The pull request is being made against the master branch

Maintainer checklist

• Assign a version triage tag
• Approve tests if applicable