Update the lab write-up for F18
Update the lab write-up for F18

This fixes a few typos, and adds and moves some text in an effort to improve clarity.

* Links to the pre-lab were changed to point to the master repository instead of the
GitHub Classroom repo. Since the Classroom repo changes from year to year, this
should reduce the update load.
* I think this finally removes all occurrences of actual lab machine names in the write-up.
* The old link to ipinfodb.com doesn't seem to work anymore (it looks like that service
just doesn't exist now), so I simply removed all reference to it.
* I turned the "to-do" list at the end into a "checkbox" list so groups can mark things
off as they go.

UMM-CSci-Systems/Log-processing,UMM-CSci-Systems/Log-processing