scoring plugin: prevent auto next+add at end of song to be logged.
scoring plugin: Classifier storing structure.
scoring plugin: make initialization work
scoring plugin: promote function and test code for classifier
scoring plugin: prevent yaml file to be open/closed multiple times. add demote function.
plugins: Add plugable feature allowing plugin to be unloaded completely
plugins: fix add/del scoring plugins
plugins: fix plugins removal, add yaml logger as a module
plugin/scoring: update yaml format
plugins/scoring: make Classifier db agnostic. load(N) dump(N)
plugins/scoring: Classifier capability as a module.
plugins/jukebox: fix classifier loading. Add missing mids on promote/demote