switch to latest Devel:Cloud:3:Staging iso
add zerofree
indent to 4 columns for consistency
remove kernel headers if guest additions successfully installed

The kernel headers actually take up quite a bit of disk which we can
potentially save using zerofree.
update and add READMEs to deal with two appliances / boxes
add SLES11 SP3 vagrant box definition
WIP idea for how to add data disks