Load the command list from an url

[plainas]

Allow passing an url pointing to the command list when launching icl. Use -u /--url. The file could contain escape sequences that are injected in the terminal. This is essentially a blatant window for remote code execution. So needs to be used with full awareness of the risks.

• For safety reasons only https should be allowed.
• Disable this feature by default or show a huge red warning each time this is used. Use an environment variable to allow disabling this security check.