Implement Initialize, Shutdown & Config

Implement Initialize, Shutdown and Config on Interop …
can be used like this...

var platform = new SQLite.Net.Platform.XamarinIOS.SQLitePlatformIOS();

platform.SQLiteApi.Shutdown();
platform.SQLiteApi.Config(SQLite.Net.Interop.ConfigOption.Serialized);
platform.SQLiteApi.Initialize();
Merge pull request #39 from sudmanche/issue35

Implement Initialize, Shutdown & Config to allow Serialized Mode in PCL