Automatically restart A::D::Cmd::Server when a file change is detected

**Which issues (if any) does this change solve? (please link them here)**
https://github.com/duckduckgo/p5-app-duckpan/issues/52

**Briefly describe your fix. Are there any important details we should know about?**
When running "duckpan server", will monitor the instant answer development directories for file changes and automatically restart the server on detection.  Caution: forking inside.

**Are you having any problems? Do you need our help with anything?**
Making sure the appropriate directories are monitored.