Final(?) round of reorg

[iherman]

Done the outstanding issues:

• incorporated George K.'s comments
• split the entry on mapping and manifest into two
• replaced the term 'version' by 'iteration'
• reordered the entries in section 2 into a more consistent order

Also did some minor editorial improvements on the fly: consistent capitalization, changed some title to make them more consistent, minor formatting changes.

Cc: @hlflanagan @TzviyaSiegman @lrosenthol @GarthConboy