Better "you need to do an actual review" message

[yoe]

Even after the redesign of the interface that @belenbarrospena helped me with, there were still a small number of people who would be confused into thinking that they just needed to approve the video without actually setting start and end points of the talk. So I did two things:

• I added a phrase to the review invitation email that basically states that review is not about approval, but about crowdsourcing the hard work
• I added an error message that appears if you approve a talk without there having been any review done, ever.

The latter of these two appears to confuse a lot of people. Luckily they go "hum, the system broke, I'll mail the admins", at which point I just go "have you read the error message? It explains what went wrong and how to fix it", which usually resolves the issue, but it's an extra round trip that can be avoided.

Currently, what people get when they approve a video that hasn't been reviewed is a wall of text:

We should redesign this such that it becomes more understandable to a user that they can resolve this without mailing the admins...