jls - Fix seg-fault and formatting

* Fix seg-fault when no IPs are configured for a jail.

* Improve formatting, increase path to 15 characters.
svc - Implement -g, -G -u, -j, -c, -m

* Implement the gid, group-list, uid, jail, and chroot specifications.

* Reformulate the jail and chroot a bit.  Remove -J and -C and instead
  introduce -m to request that svc mount devfs in a jail or chroot.

* Adjust the exit sequencing and update the manual page.