Fix crashes with image capture on VMware (and possible crashes with other drivers)

Apparently something is full of bees in the Clonezilla kernel, which causes several GPU drivers to crash during boot. These additional GRUB parameters, taken from upstream Clonezilla 2.2.0, should work around all known problem cases.
Update README.md
Update README.md
Update README.md
Skip the recovery partition stuff entirely if someone doesn't have a full set of SteamOS partitions (i.e. a custom partition layout, or dual-boot). This is the final major piece blocking dual booting.
Merge branch 'master' of https://github.com/directhex/steamos-installer
Update README.md