Add a "version" command|flag

[DazWilkin]

Google documentation references 'versions' of bdutil:

https://cloud.google.com/hadoop/bdutil#components-installed
https://cloud.google.com/hadoop/downloads#command-line_utilities

There is a version property albeit somewhat hidden:

bdutil --help | grep "version"
bdutil version: 1.3.5-SNAPSHOT

BUT bdutil has no explicit command|flag that surfaces the version:

Recommend: add a "version" command|flag