Create a page for Interactive Tool startup and failure/stop

[natefoo]

Once an interactive tool enters the running state, the Galaxy UI provides the user a link to view the IT. However, this happens before the IT has necessarily reported ports back for mapping via the gx-it-proxy. As a result, if you open the link at this stage you just receive a blank page with the error Proxy target missing.

This also happens in two additional cases:

1. the GxIT fails to run properly or crashes, and
2. any time you try to access the GxIT URL after it has shut down/stopped

So I think we need more than just an infinite "loading" type page, it needs to be aware of the Galaxy job state to terminate loading and provide you with some kind of helpful information or bounce you back to Galaxy if the job becomes terminal.