Introduce initial versions of new Command Config files.

Derive three new files from cmd_confdefs.h:
    config_bootp.h - Has BOOTP related config options, not commands
    config_cmd_all.h - Has a CONFIG_CMD_* definition for every command
    config_cmd_default.h - Has a CONFIG_CMD_* definition for default cmds.

For now, include "config_bootp.h" for compatability until all
users of it directly include it properly.

Signed-off-by: Jon Loeliger <jdl@freescale.com>