Add the 'download' buttons in sources.
Create the download corfim dialog.
Fixed #1: replace the correct the count pre page.
Fixed a error: gtk_widget_grab_default: assertion 'gtk_widget_get_can_default (widget)' failed.
Fixed #3: initialize the search box when the keyword is blank.
Add the core function of download.
Add the icon which shows resourch type of song in search window.
Use the thread locker.
Modify the download status.
Fixed #4: add custom display page group for playlist group.
Add new baidu music APIs package, and update the api version from 8.1.0.8 to 8.1.3.1.
Merge branch 'download' into develop

Conflicts:
	baidu-music.py