added option to choose ip alloc from start or end, modified gw_ip based on ip alloc option, added check in network_update to reject modified allocation pool, dnsservers and gateway_ip

Change-Id: I4551727156121eea0a9b7084c672514be0408e27
Merge "added option to choose ip alloc from start or end, modified gw_ip based on ip alloc option, added check in network_update to reject modified allocation pool, dnsservers and gateway_ip" into R1.06