[TEST] added missing wait for yellow in put warmer REST test
Added the `DistanceUnit.NAUTICALMILES` enumeration
label with the corresponding *NM* and *nmi* unit
suffixes. Update the docs to match.

Closes #5085
Update get.asciidoc

Minor improvements.

curl -XHEAD doesn't actually print anything so I've changed to use -I which actually prints the headers received.
[DOCS] improved get docs

- added _version to response
- exists call use -XHEAD with -i flag to include headers in the output
Add ability to get snapshot status for running snapshots

Closes #4946