Add the page group include all playlists.
Split all contents in do_activate to some functions. Rename the BaiduMusicSource to CollectSource.
Add a base class of source which named BaseSource, and change the CollectSource's superclass to BaseSource.
Add TempSource class.
Add some functions about TempSource.
Add favorite icon to collect source.
Add popup menu to collect source.
Add some comments.
Fix some bugs in search window.
Add comments of search handle.
Change the icon of page_group and temp_source. Modify some translate messages in po file.
Add the config dialog.
Add a api about getting all playlists.
Add a api about getting ids in a playlist.
Add a api about adding a online playlist.
Add a api about deleting a online playlist.
Add a api about renaming a online playlist.
Add two apis about adding and deleting songs in a online playlist.
Add a base class - BasePlaylist which is the base of CollectSource class and OnlinePlaylistSource class.
Add a 'delete_songs' function to the base playlist source.