Check if user is logged into cluster before deploying

[fbricon]

Proposal to fix #17

The alert box now has the warning style if there's a validation error.

[fbricon]

Session can still expire in the middle of a deployment but this change is still pretty useful.

However I'd like to provide an easy path to getting a new token and login. Ideas are welcome.

[fbricon]

Took another look at this. Basically, I'd like to get the token url similarly to oc, which discovers it from the server url:

• https://github.com/openshift/oc/blob/33f8aed30246e726258c51be27c21c60a2b005f4/pkg/helpers/tokencmd/request_token.go#L152
• https://github.com/openshift/oc/blob/33f8aed30246e726258c51be27c21c60a2b005f4/pkg/helpers/tokencmd/request_token.go#L247

[fbricon]

Now adding button to open token url for easier login