juju --version: support alternative syntax

juju --version: support alternative syntax

This makes it so the go version of juju supports the same flag as the
python version. Namely "juju --version" prints out the version, as
though you specified "juju version".

This should be sufficient to close bug #1182898.

There are some edge cases that I didn't try to solve (what is 
"juju init --version" supposed to do, etc.) Technically '--version' has
to come before the command in order to be interpreted as a global
option. For now the flag is just ignored, as the case we care about
is plain 'juju --version' which works as expected.

https://code.launchpad.net/~jameinel/juju-core/juju-version-1182898/+merge/173893

(do not edit description out of merge proposal)

[jameinel, 2013-07-10 09:41:45]

Please take a look.

[gz, 2013-07-10 12:04:12]

LGTM. Wondered if we wanted -V as well, but bzr doesn't use this and obviously
bzr is the thing to follow. :)

[jameinel, 2013-07-10 12:18:56]

On 2013/07/10 12:04:12, gz wrote:
> LGTM. Wondered if we wanted -V as well, but bzr doesn't use this and obviously
> bzr is the thing to follow. :)

I actually implemented -V, and then backed it out :).
There wasn't specifically a request for it, so I didn't worry about it.

[mue, 2013-07-10 14:04:07]

LGTM