Changes between 0.9 and 0.8
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Core:
1. Simplified the KNPluginManager.
2. Update the KNJsonDatabase module to 3.0. Support fast data reading.
3. Support clear up the image directory when loading the images.
4. Increase the write data operation maximum bound to 400.
5. Use brand new KNMusicModel module, no more QStandardItemModel.
6. Change the policy to load images from hard disk, optimized the start up speed.
7. Change the policy to parse and find files in music library.
8. Fixed the drag and drop bug in playlist caused by the QTreeView can only drop one data.
9. Fixed the crashed bug caused by use Qt::AutoConnection and overflow the call stack in the library. 
10. Fixed the proxy model sort unstable bug.
11. Fixed the library tree view bug.

GUI:
1. Support show the current playing playlist.
2. Support change the layout in different layout.
3. Support display codec of the file in main player.
4. Tweak the album art display in Artist and Genre tab.
5. Tweak the album expand size in Album tab.
6. Tweak the album display layout and color.
7. Fixed the album art won't scaled correctly in artist and genre tab. 

Search:
1. Support multiple condition search.
2. Use brand new KNMusicProxyModel for fast searching. 
3. Now search in the artist and genre won't search artists or genre any more. Will search the content of artist or genre.