politely suggest re-login if ~/.uaa/config.json is v0.0.1 format - upgrading from v0.0.1 to master/HEAD panics

[drnic]

If I've already logged in with uaa v0.0.1, and then try to upgrade to master branch I am rewarded with an ugly panic. Perhaps instead, politely suggest to the user to re-authenticate/re-login if ~/.uaa/config.json exists, but the token is invalid, etc.

$ uaa version
0.0.1

$ VERSION=0.0.1 make build
$ build/uaa version
0.0.1 aa21f51
$ build/uaa clients

panic: must supply a valid token

goroutine 1 [running]:
code.cloudfoundry.org/uaa-cli/cmd.GetAPIFromSavedTokenInContext(0x1d)
	/Users/drnic/Projects/gopath/src/code.cloudfoundry.org/uaa-cli/cmd/api_client.go:20 +0x9fd
...

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/159094181

The labels on this github issue will be updated when the story is started.