Minor changing the function of SGProcessCenter
Working on Saving and Loading's view.
Done custom the Save and Load view.

With custom transitions.
More info, see later commit.

Record game status, return status, save and load from file.
Almost finished save game part.

Minor bugs needs fix.
More info, see later commit.
Lots of content, see description for detail.

Finished saving game function.

//SGCommandFormatter
1. Add get currentLine and reload Line methods.

//SGProcessCenter
1. Only save and load line, when save or load game.

//SGSaveLoadCollectionViewController
1. Use UICollectionView to show saving and loading game screen.
2. Custom layout for the collection view.
3. Custom transition for modal to saving or loading page.
4. Add delegate method to get game status data from SGViewController.
5. Add delegate method to load game in SGViewController.
6. Add method to load game saving data for Sandbox’s Document folder.
	If no saving file found, create one.
7. Add method to get the saved screenshot.
8. Set the cells according to saving data array.
9. If no save folder exist, create one.
10. Add method to get image from saveData/screenshots folder.
11. Format NSDate to string.
12. Save game to file when tapped a cell, refresh in realtime.
13. Add method to getAndSave the screenshots to folder.

//SGSaveLoadItemCell
1. Custom drawing collection view cell.

//SGViewController
1. Save current game status when a command executed, for save game use.
2. Set segues for modal saving and loading page.
3. Set delegate for modal saving and loading page
4. Set delegate for return game status data.
5. Set delegate for return game screenshot for saving use.

//SGAudioModule
1. Put loading music file code into DEFAULT priority queue.