[CLI to sw_api] Replace SWCFG_[SETPORTVLAN | SETACCESS | SETTRUNK] ioctls.

Replace mentioned ioctls with sw_api calls (issue #39).
Implement cmd_setmode instead of generic ioctl_simple, as the CLI won't make
ioctl calls to lisa kernel module anymore.

Signed-off-by: Andreea Hodea <hodea_andreea@yahoo.com>