Add last played timestamp and "karma" rating

I would love to see the following two features:

* Please add a database column when a song was last played (or skipped). This would let me have "dynamic playlists" which add only songs that weren't played in the last X days.
* Please add a "karma" rating like Amarok 1.4 had it: Karma is between 0 and 100, songs start with 50. When a song is played or skipped the karma is updated as 'karma = (karma + percent_played) / 2' where percent_played is how much of the song's length was listened to. This way songs that are often fully played converge towards 100 and those you constantly skip towards 0.

Currently the database entry is not updated at all if not at least half of the song was played. This would have to be dropped to make these two changes useful.