Start save playlist

Get the dropped files and save locally (200MB max storage for now).
Ready this files and put on playlist. Issues:
- Big load time to ready a playlist
- Much processing on save the playlist
Change way of save playlist

Now, save with restorable File Entry. Only for Chrome 31+

http://developer.chrome.com/apps/fileSystem.html
Improve performance

Change the method > read the restorable file
Create loading indicator for playlist
Save the lastest music played

And get when open the player
Improve performance

Increasing the time of  playlist status verification
Add stringify to accept circular references
Update manifesto and player infos
Bug fix: dont load when dont have history