Default to 2G images for mesh nodes

src/freedombone-image

 VMDEBOOTSTRAP_VERSION=0.8
 MAKEFILE=${PROJECT_NAME}-image-makefile
 IMAGE_SIZE=8G
+IMAGE_SIZE_SPECIFIED=
 IMAGE_NAME='full'
 
 USERNAME=$(echo $USER)
 		-s|--size)
 			shift
 			IMAGE_SIZE="$1"
+			IMAGE_SIZE_SPECIFIED=1
 			;;
 		# Box static IP address on the LAN
 		--ip)
 
 if [[ $VARIANT == 'mesh' ]]; then
 	IMAGE_NAME=$'mesh'
+	# typically not much disk space is needed for a mesh node
+	if [ ! $IMAGE_SIZE_SPECIFIED ]; then
+		IMAGE_SIZE=2G
+	fi
 fi
 
 cd $TEMPBUILD_DIR