dhcpd: Remove our own IP from pool

The DHCP server's own IP will now be removed from the pool during
initialization.  I can't think of a reason you'd ever want it in
there and it gets in the way.
dhcpd: Adjust launch parameters

The normal launch now uses the entire 192.168.0.x range.  You can get
the previous behavior by launching misc.dhcp:default.