move all internal scripts to /usr/libexec - these aren't meant to be used directly

[Antoine Martin]

Only a few scripts should remain in /usr/bin:

• winswitch_applet / winswitch_server : essentials
• winswitch_away / winswitch_back : can be used by blueproximity, etc
• winswitch_command_wrapper : used by .desktop command lines, must be on PATH to make it user friendly
• winswitch_stdio_socket / winswitch_stdio_tcp : can be used by users for diagnosys (maybe)

Almost everything else we can move to libexec.
This is cleaner and better for packaging. Means we don't need so many manual pages.

[Antoine Martin]

Done some progress on this:

• r3502 moves the sound scripts
• r3503 moves the "kill_parent" Xnest wrapper for xpra
• r3504 moves a few more (delayed_start, server_portinfo, server_monitor, virt_server_daemonizer)
• r3505 moves the firewall script
• r3517 moves mime open

The rest is going to be more difficult to move: quite a few are called from the ssh sessions, so we rely on the commands being on the PATH...

[Antoine Martin]

• "open_remotely" is a GUI and does display an error message if not used properly.
• added man page for client in r3521

All remaining scripts have man pages, this will do for now.

stdio and tcp channels cannot be moved to libexec as we may need them to connect to the server (before the server gets a chance to tell us about paths and such)