add vlan support: vlanid/vlan dialog box and boot flag

VLAN support:
If the "vlan" pamareter is not set at boot time, it's possible to enable Vlan using a dialog box. A popup dialog box will popup to ask for the vlan_id before the network configuration.  The "vlanid" can be configured at boot time.

NOTE:  installation-images package should integrate 4 new modules: llc, garp, stp, 8021q