Add more basic unix utilities (man, less)

[benjimin]

I think the image includes aws-cli but not its dependency less. (This lack requires the workaround export AWS_PAGER=/usr/bin/more, if the decision to omit less is deliberate.) Since it is a useful default tool for scanning through text files, less should be installed regardless.

The man pages should also be installed, because this image is intended to be used by humans (who commonly need to refer to documentation).

[benjimin]

Aside from their other merits, note man pages and less are both undocumented dependencies of aws-cli.

$ aws help
Could not find executable named "groff or mandoc"