Implement new rating process

[opatut]

The current idea is that we have one major voting category ("overall") which will count into the score, and multiple other categories (especially story, sound, music etc) which can be enabled or disabled by the game submitter. These are just for feedback and will not count into the score.

Skipping reasons:

• No package available (should be automatic)
• Cannot build / run
• Unfinished
• Custom reason (textfield)

• Add humor category
• Leave empty submissions out

Replaces #60, #66, #68, #75.

[opatut]

Implemented, without skipping reasons/leaving empty submissions out, since we agreed on allowing the user to select themselves which game to rate, from the game list or game page.