Add depth coordinate to datasets

[rsignell-usgs]

It seems these datasets are missing depth as a coordinate variable.

Here's what this dataset looks like on OOICI-ERDDAP:

Here's what it looks like on OMS++ ERDDAP:

[kerfoot]

@rsignell-usgs same answer as https://github.com/rsignell-usgs/ooici-erddap/issues/9