Rename "test in progress" controller & view to "live"

It displays the current live status of the system-under-test and of the
appliance: Currently the live video stream, but it'll also have a line
saying what the appliance is doing (running a test, or not), perhaps
even logs from the system-under-test.
Add button to download screenshot

The <a> target serves two purposes:

1. Open the screenshot in a different window/tab.
2. Prevent Angular from intercepting the link (if you didn't want #1,
   you'd still need to set `target="_self"`).