Assorted cleanups for version 0.2:

emulabboot.sh: make sure tbbootconfig is executable
rc.emulab: fix exit code
register.sh: pass netbed_IP on to register.pl
waipconfig.pl:
	fix exit code
	attempt to intuit gateway: (addr & mask) | 1
	code to set netmask based on network type, but for now stick with
		common 255.255.255.0
	more exotic code for determining disk (grubs through dmesg output
		looking for disks, checks sizes to make sure they are
		big enough)
register.pl:
	use IP address passed in rather than trying to resolve from hostname
	check hash of on CD image (we may want to disable this, takes a
		long time)
	get rid of hack when calling tbbootconfig since it is now fixed