BSD support and other improvements

• Support for freebsd and many other improvements thanks to Marc S. Brook (https://github.com/nuxy)
• Added option to only block incoming connections thanks to Fathardie (https://github.com/Fathardie)
• Optional automatic installation of dependencies on the install script thanks to gloomy-ghost (https://github.com/gloomy-ghost)
• Some other fixes and improvements thanks to mean-cj (https://github.com/mean-cj)