Implement Missing Features: Shutdown, Initialize, Config 

More details on Issue #35 . Allow the Config mode to be changed, specifically to Serialized which seems to behave better on Android on iOS.

Add Shutdown, Initialize and Config to the SQLite.Net.Interop.ISQLiteApi interface.
Create concrete implementations in each platform.

Excludes Win32, WinRT, Silverlight which do not seem to have all of these features available.