Introduce env select command to switch environment

[rtuin]

With rancher config it is possible to select a default environment for rancher-cli commands.
This patch introduces the rancher env select command that does what rancher config does, except it doesn't ask for URL and credentials.

Any thoughts on this?

[deniseschannon]

I was able to get an engineer to look at this while he was on vacation and he mentioned that he wanted some syntax changes, but I didn't get much more out of the conversation. I'll see if I can have it reviewed again when he gets back next week.

[rtuin]

That's great, thanks. No stress, vacation is more important!

[cjellick]

Ping @ibuildthecloud

[rtuin]

Any update on if you'd like to integrate this feature? Does it need some polish maybe?

[rtuin]

I see @StrongMonkey re-implemented this in the master branch. Can this PR be closed then?

[cjellick]

Very stale. Closing. Thanks! Please open a new PR if there is still a relevant change.