restore command line --version flag

[holtzman]

Motivation

Version 2.1.2 of full-service switched from using the structopt crate to the clap crate for command line parsing and as a result full-service --version stopped working. This PR returns the --version command line flag.

In this PR

full-service --version will return the version number and exit, as it used to, prior to v2.1.2.

[codecov-commenter]

Codecov Report

Base: 60.14% // Head: 60.14% // No change to project coverage 👍

Coverage data is based on head (6051e55) compared to base (d961d5b).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #657   +/-   ##
========================================
  Coverage    60.14%   60.14%           
========================================
  Files           85       85           
  Lines        11999    11999           
  Branches      1957     1957           
========================================
  Hits          7217     7217           
  Misses        3133     3133           
  Partials      1649     1649           

Impacted Files	Coverage Δ
full-service/src/config.rs	0.00% <ø> (ø)

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