Like/Unlike button doesn't meet user expectation

[jace]

When a user clicks Like or Unlike, they could be indicating a preference for one of two things:

1. The speaker's presentation, or
2. The video quality, which the speaker has no control of.

Having a single button will get us data where #1 and #2 are indistinguishable, so the feedback is not useful to either us or the speaker statistically.

Instead of Like/Unlike, we should have a Rate this button that opens a panel where the user can give separate feedback on (a) content, (b) presentation and (c) video quality.

Storing this in the user's automatic playlists is a bit too much, so we should store this on the Video model.

The "Like" feature also served as a proxy for the user's favourites. It'll now be replaced by the "Star" feature. There is a usability problem with this ("Like" is a better term than "Star") but that's for another ticket.