Boost VM version to 7.2.0

created both using

ng -i 5 head1 & ./nd_createappliance -i ../../../neurodebian-images/debian-7.2.0-i386-netinst.iso -p ../d-i/wheezy/preseed.cfg.in && ./nd_createappliance -i ../../../neurodebian-images/debian-7.2.0-amd64-netinst.iso -p ../d-i/wheezy/preseed.cfg.in