* Introduced IFileStorage interface: Better abstraction than current IOConnection (suitable for cloud support). Currently only implemented by the built-in IOConnection (local/http/ftp)

* Implemented Merge functionality for SaveDB. UI is not yet implemented!
* Added tests for merge functionality

src/Kp2aBusinessLogic/Io/BuiltInFileStorage.cs

@@ -0,0 +1,104 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.Linq;
+using System.Text;
+
+using Android.App;
+using Android.Content;
+using Android.OS;
+using Android.Runtime;
+using Android.Views;
+using Android.Widget;
+using KeePassLib.Serialization;
+using KeePassLib.Utility;
+
+namespace keepass2android.Io
+{
+	public class BuiltInFileStorage: IFileStorage
+	{
+		public void DeleteFile(IOConnectionInfo ioc)
+		{
+			IOConnection.DeleteFile(ioc);
+		}
+
+		public bool CheckForFileChangeFast(IOConnectionInfo ioc, string previousFileVersion)
+		{
+			if (!ioc.IsLocalFile())
+				return false;
+			DateTime previousDate;
+			if (!DateTime.TryParse(previousFileVersion, out previousDate))
+				return false;
+			return File.GetLastWriteTimeUtc(ioc.Path) > previousDate;
+		}
+
+		
+		public string GetCurrentFileVersionFast(IOConnectionInfo ioc)
+		{
+
+			if (ioc.IsLocalFile())
+			{
+				return File.GetLastWriteTimeUtc(ioc.Path).ToString(CultureInfo.InvariantCulture);
+			}
+			else
+			{
+				return DateTime.MinValue.ToString(CultureInfo.InvariantCulture);
+			}
+
+
+		}
+
+		public Stream OpenFileForRead(IOConnectionInfo ioc)
+		{
+			return IOConnection.OpenRead(ioc);
+		}
+
+		public IWriteTransaction OpenWriteTransaction(IOConnectionInfo ioc, bool useFileTransaction)
+		{
+			return new BuiltInFileTransaction(ioc, useFileTransaction);
+		}
+
+		public class BuiltInFileTransaction : IWriteTransaction
+		{
+			private readonly FileTransactionEx _transaction;
+
+			public BuiltInFileTransaction(IOConnectionInfo ioc, bool useFileTransaction)
+			{
+				_transaction = new FileTransactionEx(ioc, useFileTransaction);
+			}
+
+			public void Dispose()
+			{
+				
+			}
+
+			public Stream OpenFile()
+			{
+				return _transaction.OpenWrite();
+			}
+
+			public void CommitWrite()
+			{
+				_transaction.CommitWrite();
+			}
+		}
+
+		public bool CompleteIoId()
+		{
+			throw new NotImplementedException();
+		}
+
+		public bool? FileExists()
+		{
+			throw new NotImplementedException();
+		}
+
+		public string GetFilenameWithoutPathAndExt(IOConnectionInfo ioc)
+		{
+			return UrlUtil.StripExtension(
+				UrlUtil.GetFileName(ioc.Path));
+
+		}
+	}
+}