relocated ControlPath to global section and ordered options
updated so sockets match ControlPath
updated ssh_config parsing and host name handling

- updated awk comparisons to be case-insensitive
- added host/hostname lookup for session display
added tilda expansion to home_regex
updated help and added required bash version
added Ubuntu Manpage: ssh_config link
moved code to host_from_socket function

- moved host_from_socket code from session_check to its own function
- changed behavior to use 'HOSTNAME' string if host_from_socket fails
- added host_from_socket to session_exit_all
ERRORs should go to stderr
corrected script name