Added copied_from_id on playlists. Fixed timestamp values in models.

core/src/main/sql/migrations/20151209054632-initial-schema-up.sql

@@ -51,7 +51,8 @@ CREATE TABLE playlists (
   last_used TIMESTAMP NOT NULL DEFAULT NOW(),
   name VARCHAR NOT NULL,
   mod_count INTEGER NOT NULL DEFAULT 0,
-  media_file_count INTEGER NOT NULL DEFAULT 0
+  media_file_count INTEGER NOT NULL DEFAULT 0,
+  copied_from_id INTEGER REFERENCES playlists(id)
 );
 
 CREATE TABLE playlists_media_files (