Update distribution version numbers

The document has very specific version numbers for how to create an
image on a specific Linux distribution.  As distributions release new
versions these steps are still valid, they just need to be generalized.
MANY document fixes

This patch fixes the following:
- Remove some outdated steps (i.e. SCSI timeout)
- reworded some steps for clarify or bad grammar
- Fix several inaccurate steps
- Fix formatting errors and ensure consistency
- Many typos