Proxy and SOCKS support, Windows and Mac OS X support, session variables handling fixes

Fixed

• Basic Windows support
• OS X support
• Improve Stegaref channel referrer templates
• Reset on channel session variables changes

Added

• Python requirements.txt
• Encoding support for sql_console
• Output redirection and inverse grep for file_grep
• Run actions on start depending from the session load
• Proxy and SOCKS support
• Unset session variables
• Show session variables