Add command to Admin CLI to get latest version

[colinmacleod]

Add a command to the CLI to output the latest version.
My specific use case: I want to deploy versions for multiple OSes simultaneously and then check PATCH is on the same version for each.
For now, a workaround is to use the "getVersions" command and pipe it to this python script:

import sys
import json
# parse the input stream as json
data = json.load(sys.stdin)
# sort the versions
data.sort()
# get the last element
latest_version = data[-1]
# print the latest version
print(latest_version)