Suppress warnings/errors within notebooks

[jlarsen-usgs]

Notebooks that have been checked in after being run and display a warning, error message, or other path as output should either be cleared or have that output suppressed if it includes an absolute path. This is a FSP requirement for publication as absolute system paths can be considered sensitive information.

[mnfienen]

right on - we should be able to make sure they are all cleared when committing. thanks @jlarsen-usgs

[mnfienen]

added a clear_all_notebooks.py script to notebooks that will simply remove all output