Disclaimer: I'll probably never do all this ...

- support fancy ext2 options
- support ext3

- add tar.gz extraction capabilities ?

- find a better way to guess filesystem's size

- UUID generation
- confirm 8192 blocks-per-group upper limit for rev 0 filesystems
  and increase if possible (bigger would be more space efficient)
- align the first block of the in-memory image with a VM page boundary to make
  it more efficient to build a large filesystem in swap.
