Initial checkin for ifup/ifdown svi config

Initial checkin for ifup/ifdown svi config

Ticket:
Reviewed By:
Testing Done: Tested with old and new bridge driver

Examples:
old bridge driver:
%for v in range(100, 104):
auto br${v}
iface br${v}
    bridge-ports uplink1.${v} peerlink.${v} downlink.${v} glob
swp2-4.${v}
    bridge-stp on
    svi-router-ip 11.${v/256}.${v%256}.240/24
    svi-router-mac 00:00:5e:00:01:00
    svi-router-virtual-ip 11.${v/256}.${v%256}.241/24
    svi-router-virtual-mac 00:11:22:33:44:00
%endfor

new bridge driver:
%for v in range(100, 101):
auto br0.${v}
iface br0.${v}
    svi-router-ip 11.${v/256}.${v%256}.240/24
    svi-router-mac 00:00:5e:00:01:00
    svi-router-virtual-ip 11.${v/256}.${v%256}.241/24
    svi-router-virtual-mac 00:11:22:33:44:00
%endfor

Pending issues:
- optimization (its slow with 2000 svi's today)
- ifquery check and running support
- names of attributes and macvlan interfaces may change after review